MOEP  The new definition of “feature creep”. Get Transmission.  
(Version 4.0)

MOEP  I personally can't stand the way song-changes are shown in the new version. (right below the menu bar)

So far I've found no way to restore the old behavior with the beautiful and unobtrusive bezel-notification in the middle of the screen so I've downgraded to 2.0.1 and don't plan to upgrade.  
(Version 2.1.1)

MOEP  Still my favourite File Transfer Client although updates are sparse ever since Coda was released.

Panic might already be working on 4.0 though, who knows!  
(Version 3.6.5)

MOEP  Incredible program.

I was getting desperate with all my image spam up to the point where I considered setting up my own Linux/Spamassassin/FuzzyOCR Mailserver to get rid of all the image-spam that the Mail.app Junk-Filter just ignores. Then I tried Spamsieve... and it's flawless.

Trained with roughly 600 emails total, it now filters 100% of all spam with zero false positives on the second day of use.

Together with the LSUIElement "hack" it's also just about invisible and very easy on the system resources.

The only minor things that I'd like to see changed would be tighter integration with Mail.app (maybe integrate it into the Preference pane? that'd be awesome!) and a different icon, but that's a matter of taste. Both - comic and photorealistic - icons don't really go with the OSX UI in my eyes, but that's matter of taste. And my icon is hidden anyway, so who cares!  
(Version 2.5)