I have the Canon HV20. I don't know about the "Vixia", but the regular HV30 is almost identical to the HV20. And the HV20 can not transfer via USB in my experience. I also have a Unibody without FW. Which sucks, considering they put it back in the next revision.
In any case, finding another computer to do the transfer is the best solution. There are products by Pinnacle (I think it was Pinnacle) that can convert on the fly through a neat little box. But that's probably expensive, bad quality, and more time-consuming than finding another computer.
Remember that on a Windows computer you'll likely be capturing it in HDV, which isn't even recognized by FCP (don't know about the latest version. I hope I'm wrong).
All this nonsense and lack of money for a new macbook has made me stick to my old Dell for video, editing in Sony Vegas Pro which is super fast on that old laptop.