When viewed on a Windows machine (whether running XP, Vista or 7; from Acrobat Reader 8 through the latest version of 9) everything runs smoothly. There's a slight delay, but layers and fields shuffle their appearances successfully. Functionality remains intact.
However, this isn't the case on Macs. An initial layer shifting might execute fine. But things quickly become sluggish to non-responsive. Fields become invisible? Apparently, everything loads as it should, but items remained cloaked until rolled over or selected or zooming in or out. Using the latest installment of OS X and Adobe Reader 9.4.0 for testing.