Yes, but the monitor isn’t limited to an Apple system. The biggest downside is that it is a Dell.
But many PC Magazine pundits have written that the best Windows PCs they've tested have been Macs. . . so neither is the iMac.
Dell makes AMAZING monitors. I use two 30” monitors, one of them the new 4k, and they are amazing machines.
The only monitors I’ve used that come close are Apple’s 30” Cinema Displays.
Ed
The iMac has Target Display Mode, which allows it to be used as a monitor. It's designed to be used on other Macs; I don't know how involved it would be to convert DVI or DisplayPort output from a Windows box to Mini DisplayPort input for the Mac, but as Swordmaker points out, it would probably make more sense to just set up Boot Camp, buy the iMac as a monitor and get a 3.5GHz quad i5 computer thrown in for free.