Yes, It all depends on what cards you have (some are incompatible, but most work) and you have to be running Win 98 or better. It's really cool cause it treats the two monitors as if they were one big monitor. When you move your mouse from left to right, it just goes on to the next monitor as if it were one big screen.
You can have separate apps running on both sides and the advantages are tremendous.
For instance, I do a bunch of web page editing and while using Dreamweaver, I can keep the wysiwyg side on the left side and full screen the html on the right side and switch back and forth just by moving my mouse. Both windows are visible all the time. That's just one possible advantage. I feel like I'm handicapped if I have to use a single monitor now. It's similar to the feeling you get when you have to use a mouse without a wheel. Once you've had it, you can't live without it.
The only bad part is that you have to designate one card as primary and that is the only monitor which can run full screen dos, multimedia stuff (avi, mpeg, tv card, etc.) The secondary card won't run it.
In my machine I've got a ATI All in Wonder PCI as my primary and a Diamond TNT Ultra AGP as secondary. If I want to play a game, sometimes I'll switch the AGP card to primary to use it for the games. No big hassle, just a reboot.
I'll be happy if I get 4 years out of these monitors. They were pretty cheap comparatively.