Just wanted to say on my system that was working with firmware 2.,8x, moving to 3.0 caused no issues that I can see (tested video MPEG2, DivX, WMV9, VC-1, MPEG4 (H.264). Audio MP3, WMA, Photos JPG).
If anything it does seem faster streaming and navigating. And Firmware 3.0 has some really nice goodies in it too...

