For the adventurous of you, there is a new version (0.6.3.2) in Extras-Devel. I've fixed some sync issues, although I'm sure there are still some left.
As usual, please make a backup before trying! Also you should not try it with your production U1 account. I once had the situation, that after a sync I couldn't access U1 notes at all.

Also please note, that synchronization of deleted message is not yet supported.

There are still some U1 bugs left as well. In short:
- Don't use the ampersand character (&) in the title of a note. https://bugs.launchpad.net/ubuntuone...rs/+bug/490969
- It is somehow possible to upload a (invalid) note to U1. U1 will not block this, and later does not allow you to access your notes. Happened to me once, but I couldn't reproduce. https://bugs.launchpad.net/ubuntuone...rs/+bug/526269
- Older notes, that have been edited with the U1 web interface, are converted to invalid XML. https://bugs.launchpad.net/ubuntuone...rs/+bug/527335

Anyways, have fun