Good points, everyone. I'd like to add just one as it is about the money...
A Mac will last many years as it is much easier to upgrade - I've only had three since 1987 - and every software update is backwards compatible. Compared to friends and colleagues, I've paid more for my hardware and software, but far, far less frequently. On value-for-money over a ten-year period, it's hard to beat a Mac.
