A possible option for people in this category (those who don't want a 24 inch screen but who don't want the 20 inch iMac either): An upgraded mac mini with a display from the manufacturer of your choice. This is an option I gave serious consideration to. Consider the Dell 2209WA, a 22 inch IPS display, that is IPS like the iMac 24 display. This display has the 178 viewing angle that the 24" iMac has.
http://accessories.dell.com/sna/pro...l.aspx?c=ca&l=en&s=dhs&cs=CADHS1&sku=320-7825
I myself never considered that option for one reason: crappy graphics card. I really really want the Ati one. I never liked the way nVidia works.