Let's face it, there are very few champions that do better in the jungle than a lane, it's just a fact that more income > less income for EVERY CHAMPION. And I prefer Kha'zix top to mid anyway, the brush makes it easier to re-activate his passive and his leap makes him a difficult gank regardless.
The fact that he's versatile enough to play both lanes and jungle competently makes him a good early pick too, as the opposing team can't be certain where you might go and thus can't commit too hard to counterpicks. --- "Pokey and the man."
I like him a lot better mid. He doesn't have enough CC to gank. Before evolving his wings I feel like it is impossible to get a good gank, and after that it is still hard. I do like that his 1v1 is pretty strong so that helps with counter jungling. --- http://i.imgur.com/QEdEj.jpg
It works, but you're dependant on teammates to initiate a gank. once you get close you can do alot of damage, but you don't have alot of options to close in. Your W slows, but it's not that reliable. Your E should be preserved for escapes and not initializing a gank. If things go sour and you get counterganked, or are generally in trouble, you'll die without your e.