Be carefull. I had an opportunity to buy a used HP 21" for $150. I was going to jump on it. I did some research first though and found it was a fixed frequency monitor. What that means is you are suppose to use a special vga card for it. Not the thing I want to do after just buying a GeForce 3 Ti500. So I passed.
On the other hand, someone is using one here on a pc and it looks pretty good. I think the refresh rate is fairly low and if you are into gaming, I would opt to go with something more main stream for the pc market.