You are correct, in that the biggest obstacle to Vista is XP itself. There is simply no compelling reason to abandon it for Vista, and benchmarks have shown that XP will pretty much run anything 150-200% faster than the same app on Vista.

So far, Vista adoption is slow... slower than XP's, which in turn came out a year after Win2k did. You are right in that there was a lot of uptake from Win98 and (blecch) WinME.

By the by, the vast majority of spam email doesn't come from Yahoo or Google... they come straight out of compromised home user boxes.

/P