And also it brings some important bugfixes:
— previous optimizations in the version 0.9.3 sometimes resulted in wrong conversations list display (one green check instead of two, some typing status freezes, etc..)
— sometimes the version for OS X 10.6 and 10.7 was crashing when trying to show a new message notification.
— version for Linux with the tray icon enabled was interrupting the shutdown process.

I hope in the new 0.9.4 those bad things are no more.

P.S. you can now toggle the notifications display right from the context menu, thanks to the open source community guys.