As I became interested in video editing a few years ago, I upgraded from a Graphite DV SE to a Dual 1.25 simply due to iMovie 2.0 requiring alot of horsepower (at the time, I was transferring many old tapes to DVD, and wanted the extra speed of the Dual 1.25).
Now that I've graduated to FCE, I simply don't need the power, speed, and NOISE of my Dual 1.25. I am seriously considering a 20" iMac for: all-in-one beauty; total wireless connectivity (my Dual 1.25 doesn't support Blue Tooth as far as I know); relative quietness; beautiful 20" display; and yes, tremendous "cool" factor.
With the extraordinary software advances of FCE and iDVD 4.0, I am willing to "trade down" to a more elligant and quiet 20" iMac. Certainly I would prefer it to be G5 powered, but IMHO I do not see this happening until at least the PowerBooks are G5 equipped. Add to that the fact that I would prefer a Rev. B G5 iMac, and it looks like I would be waiting until at least late 2005...or beyond...and what about a possible change in this famous form-factor? Personally, I feel that the new G5 desktops have lost some of the "cool factor", although I realise that these are obviously serious machines for very serious work.
Additionally, Panther has allowed the slower processors to get the snappy "feel" of a faster CPU/GPU.
If and when I order and receive my tricked-out 20" iMac, I will certainly report back to share the joy.
Hope this helps you make the right decision...