The site's pretty responsive, but some things seem to take a while (like commit messages showing up and graphs to be generated). But then again, maybe I'm expecting too much.
I mentioned it because I used it just now, because of this story, and I found it too slow to really be usable. It's, you know, a comment on the submission. Other sites are fast (e.g. HN).
If they use a lot of javascript, that might be slowing it down on my eeePC; but it doesn't seem to be javascript heavy. I wonder what it is. Incidentally, git itself is lightening fast on the eeePC.
EDIT on checking, they do have a fair bit of javascript. Most of their users, on fast machines, wouldn't be affected. A "githublite" version would be nice (like slashdot and reddit have), and might even increase sales marginally. I just tired adblocking their js, and it approx. doubled the loading speed (from 10 sec to 5 sec). Still too slow.