People say uv is good because it's fast, but honestly I don't care about that. We switched to using it for distribution of our Python-based tools because it makes it very convenient to install directly from a git repository and then to subsequently update from same repository. No need to build a package.
I tried it out successfully for the first time the other day (had 1 false start some months ago). This is after 10 ish years of system wide installs or venvs. I didn't find it fast at all. Every time I went to run the script it spent multiple seconds checking dependencies. Then one time it updated one, which luckily didn't break anything but I did get concerned. I'm sure there're some flags I didn't know to use but uvx was not great. On the other hand, it did seem to install the packages faster than pip.
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.
Maybe I've misunderstood you, but that's not a special advantage of uv. pip has been able to do this for many years.