Udyr jungle clear is fast.
but may I ask, how you gank with him. (generally, what stances do you open up with, etc.)
It all depends; because of my slight background in playing RTS games SUPER SERIOUS, I can make decisions somewhat on the fly, but generally:
If farming hard (if there's an enemy jungler that can farm quite fast as well such as skarner, shyvana, shaco, etc) I take a regrowth pendant and pot, later making it into a philo stone and turning that into shurelyia's.
If going for a early (hell even lv2) gank, or going to counterjungle a bit harder (Basically abusing a WW, Naut, Shaco or anyone else who can jungles somewhat slow), boots + 3pots.
The goal with regrowth is generally to just outfarm the enemy jungler and just ruin their jungle, because you have one of the fastest clears in the game. You WILL get boots, but they'll be later then a boots + pot start. If I feel confident about how the laning phase is going, I will generally not gank until I absolutely NEED to (mid/bot being REALLY REALLY pushed, for example. I don't really want to steal the kills the carry can easily get without me :P). I can generally get away with this until level 5-7. If I get boots first, it's generally because they don't have a jungler and I don't feel confident 2 or more lanes can hold (which hasn't been happening recently because my friend solo tops Yorick :P), so it's on me to gank.
When I usually play Udyr, the skills are Lv1 Phoenix, Lv2 Turtle(if farming) or Bear (if ganking really really early for w/e reason); from then on it's just adapting. You have to understand when you NEED things; if you need to wait a couple seconds to see how the lanes are going, that's fine, but make sure that early on if you get bear you're getting it to run away/chase for a gank. I usually put a point in bear by 4-5, but if I feel like I can get ahead of their jungler by farming really hard and am confident in my team (like in a game I played yesterday vs a skarner), I'll take extra points in phoenix and wait to take bear. If you get an earlier shurelias, you can help your team out more as well as yourself. For Udyr, positioning is KEY in ganks, If you can, get behind them so they'll have to run TOWARD you to get away safely, then bear them in the face.There are times that just won't happen; that's why you have flash! Flash and then spam the bear stance button like a pro, or just have it active before you flash if you feel you won't need the movespeed and will want that to catch up AFTER. More often then not your teammate will help you and you'll at least waste a flash or have them back; that's good because even if you didn't get the kill your team still gets an advantage by wasting a flash,ghost or heal so you can gank them later or even better having them have to leave and allowing that lane to farm freely and outlevel the other person (or people) in that lane. Generally, you don't want to get kills or to get fed; you want to play more or a tank or support/anti-carry type of role. However, because Udyr is like a swiss army knife, if you get fed you can react accordingly and play more of a bruiser role if your team needs it, getting a atmogs and other things. If you feel the team is doing too much damage to everyone else, but you're still fed, build more tanky, but still go for somewhat of a bruiser role because you can afford to. If you get fed, you can put points in tiger earlier, and if you get really fed (like 4-6/0 before 10-20 mins), just go 4 points into tiger and 4 points into turtle. You'll almost always NEVER put 5 points into tiger because it just isn't worth it compared to how awesome your other skills are in contrast, and you shouldn't be trying to dish out damage anyways.
Sorry for the giant textblock, but I guess I wanted to give you a somewhat indepth look into how I play him because I want to see more udyrs god damnit, and I want to see them roll kids.