I would only buy the 23" Cinema Display if I can see it myself (ie no mailorder). Most of the early 23" aluminum models had magenta cast and uneven illumination. Apple seems to have corrected the issue but reports of yellow cast are now appearing on Apple's discussion boards and Macintouch
Displays of iMac G5 are not in the same league as Cinema Displays. This last weekend, I worked side-by-side on a 20" iMac G5 and a PowerMac G5 with a 20" Cinema Display and quality difference could easily be seen.