See the Changelog for list of features and fixes.
Getting SoulseekQt to run on 64-bit Linux
As I've had to port SoulseekQt to 64-bit Mac, I do intend to start offering 64-bit versions of the SoulseekQt client for Linux eventually. Until then, user frd was kind enough to post instructions for getting 32-bit SoulseekQt running on 64-bit Linux. You can read them here.
Update: User Dewb wrote an Ubuntu specific guide that also shows you how to integrate SoulseekQt with the Ubuntu shell.