Backed up, took a deep breath and plunged right in. Only one minor problem, for which there is a hotfix.
I use
Firetrust Benign to filter embedded baddies from HTML-based email. SP2 doesn't like it, or it doesn't like SP2, but there is a KB article which addresses the issue
here. The hotfix worked a treat.
Edited to add: A couple of hours later I gave the lappy the same treatment, again with no problems other than the need for the hotfix to satisfy Benign. But since I'd already gone that route once, it was a cinch.
2nd edit: Also, the telephone support by MS in Australia (to get the link for the hotfix - it's not publicly available) was exemplary. One call, no waiting, no need for a callback, and I had the link in my email as soon as I hung up
AA