Definately not any 'higher end' games, low-spec games may perform OK.
But if you're a gamer, I would definately stay away from them.
If you're in need for workstation benefits, but gaming capability aswell;
the performance decrease in workstation apps is not all too substantial with gaming cards, but the performance decrease in games with workstation cards is huge.
Rikishi basically hit the name on the head. If you want to do workstation work like Cad, Photoshops, Vegas, that kind of thing you can get by with a high-end gaming card, that will obviously work well for gaming as well.
If you NEED a workstation card for work, that demands a high end workstation card and I'm talking about those 2000+ dollar cards, you're better off just having another computer for gaming.
Although sure, a workstation card will play games.
Workstation cards have a premium price because they will come with much superior support/specific driver enhancements. That is pretty much the best workstation card you can get, but I would not like to put my name out there recommending it for games. They are specific to workstation apps and are not meant for games.
What apps are you going to be running?
If you have the money to spend on that card then you must have money burning your pockets so you may aswell build two PC's, one for gaming, one for workstation.
At the end of the day, high-end consumer cards (GTX 480 for example) will run most apps fine, but workstation cards don't run games well.
Also, depending on your applications you use, I highly recommend staying away from ATI's cards. They have problems with software that uses OpenGL. I recently had a 5970 and sent it back for a 480 as I was having issues with it and ATI openly told me they have issues with OpenGL.