I have never gotten the speed argument either. Yes it's noticeably faster - but in all my projects it's 1s vs 0.1s, not enough to make a meaningful difference. Even in their benchmarks, the worst number they ever give for pip is 7s [1] (and those numbers are 2+ years old, with python's improvements pip should be doing a little better now). I just can't say I've ever cared about installing dependencies, something you do once, taking 7s longer. Nor do I care how long CI takes, it running in the background is the point.

The one use I can give it is for running scripts with inline dependencies. I have found it a noticeable improvement over pipx there. But that's more due to needing to parse dependencies every single launch, if it's something I use regularly I end up just installing them normally instead, and it's faster than either.

[1] https://github.com/astral-sh/uv/blob/main/BENCHMARKS.md