apple monitors are
1) much brighter
2) there like HD quality
3) they match all the metal styles
4) they have no deadzone around the edges
5) they have built in usb an firewire leading out from JUST one cable
6) some other monitors dont work well with apple.
If your going to use another monitors with apple, make sure there DVI, if possible.... Not a must, and makesure they have an auto config button...
I know for a fact that some monitors dont show well at all using apple.
I for example, use Samsiung Syncmaster 760v tft monitors, there old but were top of the line for their time.