There's an added bonus to being obstinate and pushing to find and use good native Linux GUI's for our major devtools: devs porting from the Windows/OSX/console worlds already have huge piles of solid GUI-based tools, and we need to find reasonably competitive native Linux alternatives. (When I say "native", I mean "not under Wine". I use Wine every day to run some old non-critical Windows programs I just can't find Linux alternatives for that I like, such as the Boxer Text Editor and Paint Shop Pro. Wine seems to run older Win32 apps better than Windows 7/8 itself these days!)
So I'm on the lookout for a git UI that is at least as good as TortoiseHg for doing the basics. I found a good Visual Studio alternative (QtCreator) a year ago after a wide search involving around a half dozen other Linux IDE's. I knew QtCreator was a good product after using its debugger for 20 minutes. It's by no means perfect but I've not had to use gdb/cgdb once since switching to it.
SmartGitHg has been on my radar, so I'm trying it out. It's commercial but has a 30 day trial (and is free for non-commercial use). This thing could be unusable -- I have no idea yet.
It needs openjdk-7-jre to run, which I installed first using the Muon package manager (under Ubuntu 13.10+KDE). The UI seems more complex, but cleaner, than TortoiseHg's. If you're already familiar with Mercurial/thg it seems pretty easy to map over the concepts and accomplish the basics. I just pushed a trivial change up using it (added a link to the vogl wiki). I'll keep trying UI's if necessary until something works for 90% of the things devs do (add files, check in, push, pull, merge, resolve conflicts, browse history, etc).