I wouldnt touch the Apple displays. Look at HP's 2229h. HD, 16:10, they rotate to portrait if you want them to. £150 each. And they come with DVI leads. And have USB2 hubs on the side. Yes just got the Mac Pro. I didnt want to wait for the new ones as i wont test Apples new products for them.
If I were going with a Mac Pro, I might consider it. However, the footprint is a little ridiculous. The giant tower sitting on the floor sucking in dust, or taking up a quarter of my desk is not appealing. I had a dual G5 when it came out, and little has changed in the tower department.
Your also talking about a 22" monitor versus a 27"...big difference.
The iMac's main strength is that its a powerful machine that takes very little room, and can be put just about anywhere.