Even though Apple said when they released the "iLamp" iMac that things run better when they are horizontal, I have to say who cares when it looks this good. Its close to the same spec of the G5 1.6 I'm using right now, so I can safely say to anyone that is looking at buying one of these that it is well worth it. G5's are a really slick processor, and nothing beats OSX!
On a side note, if they can get the 90nm G5 processor in a case that small and not worry about heat too much (the 120nm is smoking hot) then one would have to speculate that Powerbooks are not that far off, however perhaps heavier and larger than we currently enjoy.
Update: The new iMac has a FSB (Front Side Bus) speed of 533MHz for the 1.6Ghz model, where as my 1.6G5 uses a 800Mhz FSB. I feel less jealous now :) But its still a really nice machine.