Global Search ineffective
When using the Global Search to search for something fairly simple (a person's name to get a recent thread), the search feature entirely failed to find the thread. The feature also took a long time to search and felt clunky. The Global Search to me feels like a usability regression when compared to traditional email search (such as the filter search below it in Thunderbird).
DistroRelease: Ubuntu 11.10
Package: thunderbird 5.0+build1+
Uname: Linux 3.0.0-5-generic i686
Date: Thu Jul 14 14:55:52 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Alpha i386 (20110202)
UpgradeStatus: Upgraded to oneiric on 2011-07-13 (1 days ago)