I have a 1.25GHz stock superdrive eMac. At time of purchase it seemed to be the best value for money and I was not fond of the G4 iMacs (just personal taste). I had the idea that when it went out of warranty I would re-box it so that I could have a couple of extra harddrives and dual monitors. This is all possible, bt I then bought a new house and don't have time/space to do such a project.
As a machine, it was great upgrade from my iMac DV400 - I wanted more responsive editing in iMovie and so on and it was a great leap forwards - roughly 4x the speed IMO. I added a 1GB stick to as son as I could although I still tend to close apps when not in use so I managed quite well on 256MB for many things at first.
As for space, my eMac is 'pointed' into a corner and so it does not take up much more space than flat panel would in the same position - of course a flat panel display can be placed against a wall and not stick out as far.
(Bad picture of World's messiest eMac:-)
I still think it is a good machine and think the premium you pay over a PC is worth it with the OS and iLife and software bundle. If I was buying a new Mac now for my home use (iLife, eMail, internet and basic graphics) I would probably get a flat panel iMac today.