I updated to 1.8.* (Windows) last week when the app notified me of the new version and found it hugely unstable. I've since downgraded back to 1.7.0 and will be continuing to use that until I have a real need to upgrade.

It's a huge shame that SourceTree isn't open source. I'd love to lend my WPF expertise to the project; it seems whoever's working on the Windows version is a bit clueless.