Plenty of work is being done in terms of performance improvements, and almost every release features a large set of improvements. A list of all performance related merge requests that have been merged can be found at https://gitlab.com/gitlab-org/gitlab-ce/merge_requests?scope....
The slow loading of the community pictures in the background of the gitlab landing page (about.gitlab.com) gives the impression that it's very slow even if the relevant content on the page loads much faster. At this point Gitlab has a reputation for being slow so fighting this has to also be done at the perception level; not only ttfb level.
Yeah, a few folks mentioned the hosted version is fine. However, I am not interested in hosting my own instance. That's said, I don't mind paying a small monthly fee if it means getting a faster cloud service on less crowded servers.
Yeah, the feature set might be good (better than GitHub, I don't know), but every time I try GitLab or use Bitbucket, they're just so sluggish compared to GitHub it puts me off. Edit: I just tried GitLab again, and it looks like they've made good progress in this area -- still seems significantly slower than GitHub, but it's no longer dog slow to just browse source code.
We run GitLab via the omnibus package in our data centre on a modest VM and it's no slouch (2 CPU, 8GB RAM with ~15-20 users and about 10 active projects). The hosted option isn't the fastest, though.
If you'd like to help out you can read up on the contributing guidelines at https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBU....
Alternatively, any issues with data on what is slow and how these patterns can be reproduced is also greatly appreciated!