I have the same issue: too *much* physical real estate causes problems. The
24" monitor (I got an HP LP2465 on a screaming deal for $399 a while back)
pretty much takes up my entire peripheral vision.
Hmm... you may have just intrigued me to try a 24" monitor. Now I just have
to justify it to the boss :-)
Also, two years ago I had the issue that I was running through a KVM, and
it's hard to find dual-monitor KVMs.
On the KVM note, for those that have a desktop machine AND a laptop sitting
right next to one another, there is a cool utility called Synergy that
allows you to use a single keyboard and mouse across multiple machines (read
Main synergy site: http://synergy2.sourceforge.net/