There is a "Sweet Spot" for all resolutions with regards panel sizes.
I still feel that on a 1280x1024 panel that the 17" ones looked the best.
I know that everything has moved towards the 19" panels (I've seen them for around £100+vat) but I just think the panel is that little too big.
The 22" panels don't seem to offer anything over the 20" panels - except once again a larger display with the same resolution.
24" is a nice point - and to be honest I've decided that is as large as I'd like to go with regards PC displays.
Don't get me wrong, the Dell 30" panel looks nice, high resolution etc.
However where I sit when I'm at the PC and taking everything else into consideration it would just be too big - I can see a 27" display being similar.
If I'll still feel the same in a couple of years time when I'm considering the replacement of my 24" panel I don't know.
Right now, if I was given a 30" panel I'd sell it, buy a 24" and spend the difference on other upgrades.