I sit 3m (nearly 10ft) away from my PX70 and it's just right. I have a friend who has a PX60 42" in the same size room, the Pana plasmas are so good it looks just fine. The only thing I do notice is the compressed sky/freeview channels, you do notice a bit of blocking and fuzz on a screen this size and distance away, but it's not too annoying and dissapears with a good broadcast and/or HD
Panasonic TH37-PX70, Cambridge 540r v2 & 840a amps, Arcam CD92, Sony BDP-S350, Humax PVR-8000T, Sony HD-NW5, B&W CM1s, Mordaunt-Short centre/rears, REL sub