My friend on The Gear Page, Vaughn, says the tone is close enough to an actual ‘64 to fool folks in a blind test.
EDIT: Here are some of Vaughn's posts on the guitar:
The thing about the Silver Sky is that Paul Smith & John Mayer wanted to come up with guitar that came as close as possible to Mayer's 63/64 Strat in sound & feel. So, besides the cosmetic differences, the Silver Sky has a particular voice that some may not care for.
My favorite Strat of all time was an original '64 I once owned and the Silver Sky is the closest to it I've heard off the racks, including many Fenders, etc... However, if I wanted that modern, glassy, quacky Strat sound, I wouldn't buy the Silver Sky.
But we all hear it different, and that's ok too!
Well, one thing you have to keep in mind is that the target sound & feel for the Silver Sky is 63/64 era Fender. And, after playing many vintage Fenders, no modern Fender I tried sufficiently satisfied me for that sound & feel. So after running many racks of Fenders, etc. over a few years for something better than my tweaked MIM Strat, I bought the Silver Sky.
Yup, modern Fenders sound & feel different than mid 60's Strats & the Silver Sky...and you may not like that particular Strat voice. But that doesn't make it a bad "Strat". Buy what your ears & hands like...which is what I did;)! My hands & ears don't care who's name is on the headstock!
Yup, due to time we are sort of programmed to a "strat" looking a certain way. But as many variations of Strats as Fender has, they missed the niche that Mayer (and some of us) wanted in a Strat so he didn't have to take his vintage Strat on the road. The Silver Sky updates didn't mean much to me personally but the target sound/feel are right. But, yeah, its too bad Fender wouldn't make the guitar for Mayer as the traditional look may have sold even more guitars than the Silver Sky. But, then again, it might have been difficult for Fender to build a Mayer production guitar, with PRS quality standard, at the Silver Sky price point. PRS took the opportunity and it looks like they're making a decent profit on the Silver Sky...but Fender does have more mouths to feed;).