The results speak for themselves, it looks amazing, it came with the HL2 20th anniversary update, this is the same lightmap resolution:

with bilinear filtering: https://steamuserimages-a.akamaihd.net/ugc/46819323408445362/A3329F574EEA5FB2E9FD6C6D38847761E2CB4B8F/?imw=5000&imh=5000&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false

with the bicubic filtering shader: https://steamuserimages-a.akamaihd.net/ugc/46819323408421298/39A37EC811464935006C1FA42DD2DEC175033E02/?imw=5000&imh=5000&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false

try to ignore the (massive) exposure differences as I didn't have the same gamma settings and hdr settings when I took the screenshots, but look at the difference in lightmap quality!

this would look phenomenal in newdark.

ZylonBane
The shadow maps look quite a bit better, but OK.

These aren't exactly the greatest screen shots either.

The Source engine bakes its lighting too. And it, like Dark, always bicubic scaled its lightmaps, since that's the default method 3D cards use for texture scaling.

This new lightmap scaling just appears to apply slightly more blur to them so the pixels aren't so obvious, and does some other processing to ensure the additional blurring doesn't result in lost shadow detail, which appears to cause some shadows to become thicker.

Edit: Actually strike that on the shadow thickening; the two screenshots above just weren't taken from the same position, for some stupid reason. I've tried toggling this myself in the updated version and it does appear to merely blur the lightmaps a bit more than vanilla bilinear stretching does.