Rest assured I'd never come to your house and pick up the guitar and tune it. Not unless you opened your wallet first. I get paid for that.
But it has always amazed me that some people can pick up those things, pluck a string and just based on the sustain tune it to the perfect pitch. They have a gift called perfect pitch (which I've been assured by many people who have it is also a curse). It's a gift because most people don't have that ability. So, unless you do, don't do it.
Having the strings frequencies align doesn't mean crap if the first note your using as a reference is not correct. You are only making the entire instrument out of pitch.
With the locking strings, the guitar rarely goes out of tune
I call B.S. which is why I don't know a single professional player who plays such an instrument - which if it worked would save them the $300 a night (plus per diem, plus, plus..) they have to pay someone to stand there and do it for them. The more you play it - and the harder you play it (and the harder you play it, the better it sounds) the more you're changing the tuning. Weather - both temperature and humidity - has an enormous impact on the tunings. It keeps the pegs from slipping and detuning that way, but if you have a really good guitar (Martin, Taylor, Gibson) it has pegs that are machined not to slip, so its only a problem on the less expensive models.
(And I'm not dissin the less expensive guitars, I got one myself, because hell, I don't play good enough to justify a really good one. But I have been able to play some awesome instruments and yeah, oddly enough - and I'm sure it will amaze anyone - that a $3,000 instrument is a lot different from a $100 instrument. In that, guitars are a lot like hookers.)
So, if your hanging out strumming Michael Row the Boat Ashore, or finger picking Wish You Were Here, a good guitar can stay in tune, and the tune-lock works because, like I said, its the pegs slipping not the playing that make cheep guitars go out of tune so easy.
But, if someone like Jerry Garcia shows up, it ain't going to work. Old Jerry used a 2mm Graphite pick, which is like playing with a quarter. Most plays like the 'medium' which tend to be .70-1mm thick, and even those will mess with tuning if you play hard (and remember, hard sounds better). But if you have some big biscut like Jerry playing that with a 2mm, your going to (or Jerry will, he did have near perfect pitch) retune it every song or two.
And of course you ASK first, you just don't pick it up. Really. You don't do that with anyone's personal property. I can pretty much guess that anyone who would just pick it up without asking is a dolt, not a player. Any player want's to be asked about his/her guitar, and returns the favor.