I'm currently using Thunderbird 3.0.11 - just for Usenet - not emails (for which I use Outlook).
It's currently offering to upgrade me to v3.1.10 but, having been caught with the upgrade of Firefox from v3.6 to v4 - which totally screwed up my browsing experience until I had worked out how to make v4 look like v3.6 - it's a case of "once bitten, twice shy" as far as Mozilla is concerned!
Have any of you upgraded TB to v3.1 and, if so, are there any gottyas?