Thanks. Well, I'm running Mail, Safari, iTunes, Contacts, Pages, Evernote, and 1Password.
I am most suspicious of 1Password and Evernote, since they're the only 2 not-Apple applications. But I don't want to lose my notes in Evernotes and I really can't lose my passwords in 1Password, since it makes them up for me and I've no idea what they are. Maybe I can start with the 1Password Safari plug-in.
I have downloaded AppCleaner and spent a satisfying 30 mins uninstalling things I don't even recognise or remember and deleting them.
I am tempted to try the beta 10.8.2, but worried that will create more problems than it fixes, being a beta...