I'd like to add my two cents. I also agree with many others about limiting features. I don't mind obfuscating some more dangerous features in some kind of an "advanced" menu or something, as long as I can get to it. This is the absolute number one reason why I HATE the official Github mac/windows client. It hides A TON of stuff, including push & pull (which is really irritating). Whenever I am forced to drop to the command line it lessens my opinion of the tool.
I know what I'm doing when I force push and I really like sourceTree. Please add the ability to do force push. I don't care if it's in blinking red text that says the world will explode if you use it, just add it please. I don't think it's atlassian's job to make sure I don't make a silly mistake; I think a clear warning message would be just fine.
I do want to give props though for creating the aboslute best cross-platform git GUI I've yet to use. I'm so glad there is a "fetch" button at the top instead of just "pull". You guys have done a stellar job of putting all of git's complicated options into a nice interface that's easy to look at. Now if we could just add in some of these things that you deliberately left out I would be a very happy customer. I'd even be a paying customer for this product if there was such an option. It's that good.