Two well known open source products got a major release out in the past couple of days: Thunderbird 2.00 and Ubuntu 7.04
I'm a big fan of both products and have been using them for quite some time. I've updated Thunderbird this morning and it feels a bit faster and looks cleaner. I think I'll wait a bit before upgrading to Ubuntu 7.04 to see if it brings any problems. A mail client is less time intensive if something goes wrong compared to an entire OS.