I've had three guitars now with stainless steel frets, very subtle tonal differences, but just a tad brighter, but you don't really hear it by the time you wind it up to moderate gain, I had 2 Les Paul's identical pickups in the bridge, took one of them in to put jumbo stainless steel, I ended up with Jesscar SS 0.090 x 0.055", it was a dramatic shock how much I enjoyed playing the guitar. Tonally seemed to be no important difference. but what a difference to the feel. you do have to slightly adjust your touch, but within 15 minutes of playing I just felt like I was a better player all of the sudden.
unfortunately the Les Paul was a 13 pound beast and eventually it moved out of the stable, but I had a telecaster refretted with stainless steel jumbos, and I bought a warmouth flame maple strat neck with stainless steel jumbos (just gorgeous), I just love the greasy feel,
I would prefer if every guitar I owned had them. I'm pretty sure that's where the term the guitar bends and plays like butter came from. They literally feel like they're covered with melted butter. enables me to cover David Gilmour songs with ease three-step bends, no problem silky smooth. I think what I picked up from Paul smith video is the extra hard fret wire makes manufacturing much more difficult, the finishing tools become damaged more quickly and getting the stainless steel to curve and match the fretboard radius takes a lot of extra care and effort, and he doesn't see a high value in the playability or the longevity factors, as well as quality control issues, so I think he's looking at it from a balancing act standpoint. if players demand it for personal feel, I feel like he would consider allowing it as an option,
I was warned by my luthier, that if the fret wire popped up on the edges within a few months to bring it back, because it's more difficult to get the fret wire perfectly bent to match the radius, and on a re-fret job the grooves are now slightly more open, so he also superglued them in.
I have had no problems or complaints with any of my stainless steel fret guitars, joy joy joy.
but my PRS 594 leveled jumbos also plays extremely nicely, not quite as silky as pure stainless, but because of the PRS attention to detail such as fret polishing, with the regular nickel steel alloy still feels amazing. but I also believe certain manufacturers make harder fret wire as Paul pointed out. so he probably uses some alloy that's very close to being as hard as stainless steel. so he may not believe pure stainless is an improvement worthy of the extra problems.
? I'm confused?
So now you owe me a Nancy or Sally! Go ahead, I deserve it. 
