Yeah, there are always limits as stated above. But you have full control, the language is about as full featured as any programming language, in some ways more so due to easy sprite and background drawing functions, built in collision detection, rotation, scaling, music and sound effects etc.
In other words it's not simple like Warioware D.I.Y. If you are willing to put in the time, you can create some really cool stuff.
Comrade UncleSporky rights. All depends on the programmer and patience. On PetitCom your can make very good a games and programs.. best examples PX7, Tiny Xevious DualEdition, Performance Nebure!(JAP) and more.
Other than the hard code limits I've had lazy code cause slowdowns (at 60 FPS), so really no limits beyond what a game developer would face except you really don't have any diagnostic tools to see what the hard ware is doing.