That's a bit of a loaded question for a few reasons..
Shaco is often banned in lower ELO's, which means that in ranked play, while he may be a devastatingly powerful early game champion, he's not a reliable pick for ranked play.
In normal games, he is played and can be played effectively, however, as insinuated in your post, his early game is very strong and his late game is rather iffy. After early/mid game, he's best used to backdoor enemy towers/inhibs and bait teamfights with his incredible escape mechanisms.
Your objective as Shaco should be to gank enemy lanes early and often and get teammates as fed as possible before mid game erupts.
Mundo is a better overall champion.. He has great jungle speed, wonderful counter jungling, and is incredibly difficult to deal with. His ganks are mediocre but he is very useful mid/late game where he effectively becomes an initiator and damage soak for his team.