I've been using Vista at work for the past week, and looking at OS X I need to say there is no rip-off that I can see by Microsoft. Vista's look and feel are entirely different except for a couple of probably coincidental display effects, which any designer would have come up with.
After initial setup in the computer room, I've moved the box down to the kitchen counter where it isn't in the way. Will play on it from time to time just to get a better feel for it. One thing I immediately do not like is the lack of a scroll wheel on the mouse. I can live without the left-click, kind of.