I agree that github's bug tracker is quite limited (for some reasons that I cannot pin point, bug tracking seems really hard to do: that's the only example I can think of of a fundamental part of any developer toolbox that has no great open source implementation).
As for launchpad UI, code browsing is indeed the worse part, but I find the whole thing difficult to understand. For example, we created a page for scipy quite some ago (https://launchpad.net/~scipy), and still today, there is no hierarchy in the information. For example, where can I download the software(and I do mean the releases, binaries if possible) ? A lot of the UI space is spent to convince me to subsribe to the project, or give me information that I really do not care about if I just want to use or install the damn thing for my users if I am an admin.
Also, stuff like email UI to subscribe/create bug has been horrible for a long time in launchpad(I have not checked recently, maybe it has been fixed).