Mundo was my favorite champ, i have like 66 ranked games with him last season.

I think he really needs a rage bar or a 2nd resource source like Morde, Shyv, Rene or just let him use CD like garen.

There are so many items mundo needs like merc treads, spirit visiage, atmogs, FoN and then he is finally built to kill!

He honestly sucks as* before he gets his build ( in early game) because in order to harass and kill minions you lose health, and then you are harrased on top of the health you are losing for your skills.

But Mundo in general sucks...

He is fun if you get fed..

With a Regrowth Pendant, a couple regen Quints, and masteries you can sit top all day last hiting with cleavers and harassing with no problem. He can out farm most tanky dps top without fear of any reprisal, but you kinda have to be passive till 6 at least.
I love him so much, but he still does seem to fall off late game. A champ like Nasus provides more damage, lives longer, and has a shut down cc. Sadly, Mundo needs a bit of a rework, but I still play him a lot just to smash faces

heyho, i have 2500games as mundo
look at this video guide:

http://www.youtube.com/watch?v=bd_czb8KPsE

it may help you, when you play mundo

hes a bruiser like most solo tops he has a peraslow with his Q u cant run from him his w maks cc almost useless on him and his e is the best ad steroid in the game r+w run into a team fight and destroy there carry hes built tank but isnt really the tank (kinda like garen)

As far as I know, Mundo is currently severely underpowered and is in a bad place at the moment. Trying to figure him out now won't do much good until he gets some buffs. :<