Sourcetree slowed down significantly with the recent visual changes in 2.5 and 2.6 only barely improves this.  The diff viewer can take upwards of 30s for to view the changes in a small file.  Staging a chunk can take 15s.  I've reinstalled freshly but to no avail.  The code base has around 70k lines of C++ in a few hundred files.  Sourcetree < 2.5 coped just fine with this.  Now, it's practically unusable.  Worse still, the performance gets worse the longer the application is open.

I see a lot of the mac spinning wheel while I wait for simple interface actions like the context menu to appear.  I see the animated circle of lines on the file tree too.

I see these problems even on small git repositories, but it gets worse with larger repositories.

The basic functionally is severely impaired by the poor performance. This application unfortunately now is the least responsive application I use.  

I really like the ability to view and stage code chunks, but I'm unlikely to continue using sourcetree if I have to wait 20 - 50s to stage chunks of code.