I agree with Toon about the size. It's really the quality and color that count. Why buy a 30" monitor if it's a piece of junk (I'm not saying yours is junk), but don't go out and purchase a big monitor because it's big.
My husbands G5 has this monitor
Cintiq 21UX Product Information. One of our clients gave it to us as a gift. I use the standard 19" Mac Monitor for my G5.
At one time I had 2 monitors...one for my pallettes and the other for my layout work. The advantage of having a larger cheap monitor (like the 30") is that it's great for publication layout so you can see two pages at a time. But if you do this, get a great monitor for color correction of photos.