It sorta messes up my game, but that's all I know.
Offline
Scratch executes each block as a frame. Normally there are around 30-40ish frames per second.
Turbo mode speeds things up by executing more blocks per second. However, if there is a wait _ secs block, it executes it normally by waiting that time.
So if you depend on Scratch's frame rate for the timing of your project, it may get messed up in turbo mode.
Offline
Turbo mode just speeds up your project (I believe you shift-click the green arrow to activate it).
Offline