I'm at Trinity and I use a laptop mostly, but I know people who have desktops as well. A gaming PC should be fine, i'm sure most of the compscis have them.
Also, i have a daily limit for internet stuff, and if you use too much you get cut off for a day. I've never reached it, but I know people who use a lot of video skype or stream live sports for long periods who have been cut off.
I've used regular skype before and had no problems.
They really hate p2p software though, and that gets you cut off too, so remember to stop all that **** before you come to cambridge.