I do have a 2002 R8 Les Paul that had factory frets when I bought it, and did not noticed any tone difference at all when the guitar is plugged in, after I had the frets replaced with medium SS frets. It stayed pretty much the same on both clean and distorted tones. Matter of fact, this particular Les Paul had a very nice, smooth top end, with very punchy midrange and very focused and tight low end, compared to my other Les Pauls, both before and after the SS were installed.
I has a pair of Alnico Pro 2 humbuckers, which are low output, in it, and this combination it's just incredible in this guitar.
The fret job is just incredible, and was done by Eric's Guitar Shop, in SFV. My all time favorite guitar tech for fret job. No bad spots, ghost notes, half ass polished frets... his work is flawless.
That makes the guitar play perfect, and the tone and intonation to be at it's best.
I promised myself I'll only use SS frets from now on. Specially on my vintage guitars.