I used the nokia supplied wizzy tool (PC Suite for Nokia 6600) to copy over the details from my old phone. Annoyingly, it's a little bits pants. While it copied my calendar entries fine, any phonebook entry with more than one phone number had all but the first silently discarded during the import, Nice! Luckily I spotted that one, and was able to zap those few entries over using Bluetooth.
My big gripe, however, is that the import app doesn't import any of your SMSs. What's more, the phones have no option to resend on messages via Bluetooth, only via sms. Oh, while you can copy SMSs from the sim card onto the phone, you can't copy them back, so that route of migrating them is out.
Since the Nokia tools were so useless for SMSs, I decided to go play with the Linux ones. There are two options, Gnokii and Gammu. Both have varying levels of support for the Series 60 platform, and neither quite works.
Both offer my basic information (via the AT command set). Gammu offers the possibility of being able to grab the SMSs directly, but I can't set up an appropriate connection to do so. Gnokii is going down a different route (with an app you run on your phone to grab the data, and present it to the library in a similar manner to the older phones). This isn't quite finished yet, and doesn't currently do SMSs (though when it does, it'll do them perfectly, since it'll have access to the underlying messaging API).
So, I've emailed the Gammu list, asking what config options I should be using with their series 60 support. Failing that, I'll just have to wait on the Gnokii developer (who's quite friendly, he's emailed me about my series 60 page...) to finish the client side app. I'd try it myself, but I don't think I've really got the spare time to learn Symbian C++ any time soon :(