I can confirm that the O2 UK settings on the wiki are right and I've removed the "''(Settings Unverified, please update if wrong)''" bit.

A few things I've noticed (I suspect its mostly repeating what others have said but anyways)

I'm using version 0.2.1
- I do get a notification on the New Message window but not on my conversations inbox widget Not that I'd expect it to right now since that would mean linking in to the conversations inbox - which would be great but I'm sure thats a few steps off!
- If you have an entry in your address book with no phone number (or the number of 0) then that will appear as the "senders name" with the actual senders number next to it. Deleting any 0 number names in the address book fixes this.
- There's a definite delay of receiving messages (a few hours) Mind you normal MMS can be a bit like that too
- The pictures are very small size, almost unviewableI know people have said this before
- Would be nice to be able to search address book via typing the name I think I've already read that you are looking in to this.

All in all a big thumbs up from me, MMS was something that I really needed on the N900 (since my mum has got as far as MMS but not quite to emailing photos!) and it's great to see something in progress already!