Usually uv pip is only about x2 as fast as regular pip for me. Occasionally I'll have some combination of dependencies that will cause pip to take 2-5 minutes to resolve that uv will handle in 10-20 seconds.
The impact of a 2x speedup is relative. For a quick test on one of my projects it's 10 seconds with pip and 4 seconds with uv. That's roughly in line with my previous testing. It's a nice minor speedup on average. It really shines when pip does some non-optimal resolving in the background that takes a minute or more.