I get the same "no /Dev/PMU device found" message and have been looking for a way to remove it but have found none so far. The posts I've read on it say that it's in a conf file but I haven't located the one it's in yet. From what I've read it has something to do with Power Management Utility and has little to no effect on the operation of Gnome. As for mouting, I use an SD card (4 Gig) to play the movies off so I simply go to /media/disk and open the files. I also like how VLC has the option to "Open Directory" command.

My goal in installing linux was mainly something fun to play with after spending all that money on an "expensive toy". I haven't had the time or the drive to dive too deeply into using linux on the PS3.