Figured I'd give it a try this evening and wasn't expecting it to run that great given one video on youtube showing it running under 50fps on a 5080 (I have a 4090), but here we are, with DLSS Quality and Frame Gen (no noticeable mouse latency at all) it's pulling ~90 fps and feels as responsive as HL does pretty much. It's in need of proper optimisation though, changing DLSS to Performance makes no difference to framerate, but it is work in progress so can excuse the bugs.
The mod only covers the first few areas of the start as well just to give a taste.
More screenshots:
https://i.imgur.com/dfoxY7M.jpeg
https://i.imgur.com/m7Yjdmp.jpeg
https://i.imgur.com/8Ddh5ce.jpeg
https://i.imgur.com/gbjVglq.jpeg
https://i.imgur.com/6D9oHNS.jpeg
https://i.imgur.com/3STzkzq.jpeg
https://i.imgur.com/jav0uDB.jpeg
https://i.imgur.com/kyhrK4P.jpeg
https://i.imgur.com/3ilj59U.jpeg
https://i.imgur.com/OSKscsG.jpeg
https://i.imgur.com/IhtayEN.jpeg
I can't wait for the full HL2 RTX release now as that is going to look so good.