I have used the DMK with Vista, works fine and drivers are compatible.
I went to the Skynyx as a stop gap for the next year or two. It is a better camera than the DMK for several reasons. Noise and well depth are two on the top of the list. Skynyx has very low noise and this results in the images I have been attaining. The well depth is greater and this means that more detail can be obtained by fewer frames. There are other side line benefits to great well depth too.
I did think of getting the Point Grey camera that Anthony uses, but I think things will change fairly rapidly in the next year and did not want to spend that much money.
Fire wire is good because of the speed in data transfer. With the Skynyx I have found that while I can get high speeds on Jupiter (45fps) it does tend to get a bottle neck with the USB 2 format. I never got this problem with the DMK. It can be sorted by using a RAM drive, but this is more software that you need to install.
Generally though I like the way the data is collected in the Skynyx and can recommend it as a planetary imaging camera. If you don't want to expend a lot of money go with the DMK because as Mike said there are other things that need to be bought also.
That machine would be fine.
Yes DMK comes in colour and mono. Check out the Imaging Source pages.