Typing on my phone so Ill make this brief, I dont recommend putting anything on the sd card at the moment. The reason for this, is that on a froyo upgraded captivate, an aplication shortcut on your desktop will dissapear after a restart every single time if it is moved to SD card. This is especially annoying for me with apps like angry birds that wants to move to sd card every update.
Edit.. I just use the sd for music movies and rom data.