I've had all sorts of upgrade problems going to lucid from 9.10 via the Distribution upgrade system but I've got a working system now.
I use the New Zealand iHug repository and several of problems that I've had indicate that the lucid binaries are out of date (from March rather than the latest release)
Heres an example of a discrepancy:
I performed all upgrades available on the iHug repository and then when switching to archive.ubuntu.com I had 944 packages to upgrade.
I'm really worried that other ubuntu users in New Zealand may be finding the issues I had. First time I restarted my mouse and keyboard weren't working at the login screen. I had to go into recovery mode, remove openoffice due to some kind of cyclical dependency, then do a apptitude full-install to fix it.