I wouldn't buy it, but not because I hate the old G4 iMac design. Actually, I think that's one of the best ideas Apple ever had and really want to pick one up second hand when I've got a few quid going spare.
Reason for not buying is simple - proportion. The old model had, what, a 15" screen on it? And that matched up perfectly to the base. In order for this design to work with a 24" screen the base would be a LOT bigger and throw the whole thing out of whack. I'd also be really worried about an arm being able to support the weight of a 24" panel properly for the entire lifecycle of the machine and just can't see this being stable. While I keep my electronics out of the way an iMac is going to be 'on display' to a certain extent and I dread to think what would happen with just the smallest of knocks...