Well I got 50 yesterday, and wrapped up all the soloable quests in un'goro except one or two maybe.
One quest there is a MUST DO
http://www.thottbot.com/?qu=3844
I started this quest at 50% into level 49 and finished all but the final fight 30% into level 50, and the final fight gives over 7k xp and sweet rewards.
This quest also leads you into Felwood, which is where your 50th Warlock quests begin, and there are a ton of other quests available there. The only rough bit is you are held up there for a while factioning in order to pass thru the tunnel to winterspring. I think it takes about 3 hours of killing deadwood furbolgs and doing the 2 quests involving them to gain 'unfriendly' faction and pass thru unmolested.
This is about a 20 step quest chain, and probably gave close to 50k xp all totaled.