Not bad at all.
This is a pretty nice game. It runs smoothly and boasts great visuals. The only issues I saw related to controlling and costume variety.
The controls themselves are good, but the jump needs work; Sponge and Leroy lacks a solid response time. The jump button rarely responds on time, leading to missed platforms. Perhaps if main character ran slower, or simply jumped on time, this would be a solid Flash game.
As for the costumes, 80 objects are advertised, but many are repeats with a slightly different palette. Most choices are simply unexciting.
Overall, this is a great project with plenty of potential - Keep it up!