I use git almost exclusively from the command line, but for visualizing the state of several local/remote branches, gitg is unsurpassed. One can certainly do without it, but it is a very useful tool to have around. I think it also especially helps in a teaching context. Operations like "rebase" (slightly evil, but necessary with git-svn for instance) are much easier to explain if someone can see exactly what it did to your commit graph in the GUI.

Thanks,

- Peter