I agree (http://www.quora.com/What-online-tools-do-scientists-wish-ex...). Why don't we just start using GitHub itself to do this and go from there? The pain points will suggest ways that a real science-focused github could improve on GitHub itself.
If we want non-programmers to use git, we need GUI's to instantly visualize the state, commands and other possibilities. No non-programmer is going to learn git using a CLI.
Not that I'm disagreeing with you--But making git point-and-clickable doesn't strike me as being very simple.
I think that github is such a good tool to interact with git repos that if they made a version that can work locally (the main difference is explicitly dealing with the index and the current tree) I'd use it to manage git projects in a heartbeat.