On x86 you may have problems with ati's binary drivers with xorg-7.1, but these drivers don't even exist for ppc. And the open source radeon drivers work great. The migration guide covered all the other issues.
Well, there is no problem but I want to keep my current kernel to avoid multiple changes at the same time.
At the begining I was using 2.6.15 because of ivtv driver which is not working very well with 2.6.16.
But now I've changed my PVR 350 for a Pinnacle PCTV so I guess this is not a problem anymore (in fact, the PVR 350 is now used in a PC media center with XP - shame on me :-)).
That is true, KnoppMyth looks cool. However, with windoze MCE you get Drivers for EVERYTHING and it works out of the box... even with Knopp Myth if you dont have certain equipment it can be very hacky - check out the forums on the site.
Well, if you are building some kind of pvr/stb and only need it for that you would be ok with Windoze MCE on it and MOST important it works OOTB. Not everyone has hours, days, and sometimes weeks to fix linux bugginess and google docs for days ;)
Peg makes on ideal box for this but you have several problems:
1. Compiling dependecy problems with MySql and Mythtv