Well the new patch has brought us a lot of goodies to play with most noticeably the new champion, Karma and Udyr. I haven't played Karma or had much experience with her so I can't really say much about her. On the other hand both Udyr and Zac have been popping up in games here and there and I can give my opinion on them and feel rather confident in some strong first observations. I've played both as well and can indulge my opinions of them with overall strong jungle experience. Due to LoLreplaying dying - I don't have any updated footage of either of them.
First and foremost the new Udyr is definitely a different yet similar beast. I'm not sure how to go about describing certain things but his power in certain aspects has been relocated.
Mobility - It's outright insane right now. Udyr, with his new passive and levels in bear, just zooms through the map. It's insane how much ground Udyr can cover in short time. His little gap closer (albeit bugged) is also insanely useful for ganking. No more will you miss a bear slap because you were a hair away from the slap.
On the contrary, Udyr still suffers from the issue of being kited like hell. This doesn't seem something they'll ever fix. It's made worse by the fact that League of Gap Closers still laughs at him at every chance it gets. Udyr became much stronger at ganks but his team fighting is still botchy because of kiting.
Pushing - His pushing has always been insane but dear god did the change just send it spiraling into stupid mode. I tried my experimental split push build and a wave was basically insta-gibbed whenever it popped up. Nashor's Tooth Udyr was amazing at pushing (meh at team fights) and there was almost nothing the enemy team could do about it. I'd run if they came to fight me and then just go back to pushing.
On the contrary, despite having his stance costs lowered he is running into mana issues early. It's gotten pretty bad in some cases and I even had to rob a second blue in order to sustain my mana hunger. I think this still needs a buff of some kind. He is very starved without mana regen early and even into mid game. Spamming abilities in order to push will destroy him early.
Clearing - His first clear is still relatively the same in both Phoenix and Tiger. He takes more damage due to not using Turtle as much or having increased resistances. However he starts clearing at an insane pace (better in Phoenix) the more ranks he gains in his abilities. He becomes much faster than he ever was.
On the contrary, his dueling did take a dive as he's weaker in a straight out duel vs other junglers now. Tiger is relatively unaffected by this and only really takes more damage now but can stick to someone better but Phoenix did become noticeably worse. The bonus stats from Phoenix helped Udyr slap some opponents around and was more useful than the Phoenix fire vomit when dueling. When I picked a fight with a fatty this became quickly apparent and just backed off before his teammates arrived. Phoenix's dueling definitely became weaker though going from S rank duelist to A rank duelist isn't a bad thing.
Though on a note that is just flat out disappointing is that his builds are still on the more expensive side. He either needs a lot of murder gold or insane amounts of farm to get going. His split push build seems to be rather inexpensive but it's really not that strong for team fights unless you can somehow not get focused. His mana issues (which remain for a good part of the game) demand that he get some form of mana in some way. That directs him into certain builds whether he likes it or not.
Overall I can't really say if it was ultimately the best buffs but they feel nice. I at least have better chances of obtaining murder gold and using items to pad some deficiencies now.
As far as Zac goes he so far feels rather powerful. In my opinion he leans towards the potentially overpowered side. I'll just do a quick breakdown of the usefulness of his abilities and some of his aspect strengths. His recent buffs before release definitely helped him as he was underwhelming in his first iteration.
His passive, the healing portion of it, is really stupid. It doesn't help him jungle or anything really until much later on when it wouldn't matter. It's not relatively useful in fights either because of all the pandemonium. However his "Anivia passive" portion is great for turret diving obviously and it's also great for baiting opponents. What else can you say about a Guardian Angel passive?
His Q is pretty much trash. It's crappy range and animation screw it over. It does almost does no damage and, as a result, I just leave it at rank 1.
His W is his bread and butter damage ability and helps his clearing speed immensely as it gains more ranks. What else can be said about % health damage? It definitely deals hefty damage the more prolonged a fight is at the cost of his own health.
His E is just stupidly good. Hel his entire ganking aspect will be condensed into this explanation. I rank E up first (though I put 2 points into W first) because it increased the range of his slingshot. It's amazingly stupid. The range you get on this allows you to do some really silly blink ganks and avoid tons of wards. Direct ganks are possible as well (behind your tower) which means the enemy won't see you coming. In a game where being caught off guard just once can result in death, this is a very powerful ability.
His ultimate (in combination with his slingshot) potentially make Zac the most powerful direct ganker in the game now - replacing Hecarim. He can slingshot directly into a lane and pop his ultimate thus being able to chase down practically anyone. Zac's own damage is pitiful so he depends on his lane mates to murder the target. Still if he has a powerful lane mate like Zed or Kha Zix he'll grab the target and make sure they die a bloody death.
Like I can't even exaggerate this. The incredible range he has with his (ranked up) E and his ultimate is absurd and it pretty much guarantees you grab someone. Unlike Hecarim, Zac doesn't give a wide reaction time to his gank. It's basically like "whoa wtf?" and then splat. You have to have pro level reactions to see it coming and even then he'll likely still get you.
Zac is an incredibly awful duelist though. I found that quickly enough that he'll lose to almost any jungler in the game. His type of jungler usually sucks vs others in straight out fights anyways so it's not that big of a deal. Just avoid fights early as much as you can especially vs junglers with a lot of maneuverability.
Zac's sustain is pretty shoddy early but it gets better later. There's not much to say here really - his natural health growth will eventually make his passive better.
His item choices is where I'm having a hard time. I'm leaning towards building him as an Magic Pen/Tank similar to how you'd build an Elise. I can't consider him a true tank as he has no real ability to peel or draw aggro. He's amazing initiator and then he simply just tries to deal as much damage as he can before he explodes. His ultimate allows him to CC the entire enemy team (if done right) or just sit on top of the enemy carry. He'll likely die quickly if he does that though so I've preferred to have him just as an initiator and brawler (frontline) vs the other fatties. I have yet to try him with a pure tank build but I don't feel it would work great on him compared to other junglers like Xin Zhao or Jarvan.
TLDR (for the above) - He's great for initiating and then just eating the frontline with a magic pen build.
Overall I think he's a great addition to the tanky gank junglers. Overall they all seem to be ability power based and damage all relying on health in some way...which is usually on their Ws. Well hopefully Riot becomes creative with the next ones. Zac was buffed before release so he definitely feels better and hell I may even say he's probably overpowered. Gankers who give almost next to know chance of reaction (or proper reaction) tend to get nerfed.