TAXI.com

Howdy, guitar players (acoustic and/or electric) - although I'm mainly asking about playing rhythm acoustic guitar;
still glad to hear from you electric lead/shredder players, too.

There are lots of reviews on You Tube, but I've never seen anyone using this device.
It's been out for several years, so there are already upgrades and several versions of it.
It's about $50 online - but not sure it's an experiment with a significant R.O.I.
Wuddyathink?

String Butler
https://www.youtube.com/watch?v=L0TEwNch2ZA

I'm in some guitar forums, and word is, it works, but you should see a luthier or a good tech to make sure you're not masking a poorly cut nut, binding or burrs at the bridge or some other issue. If you're still experiencing tuning difficulties after a checkup, it's an effective last resort; I think maybe Gibson buyers are such traditionalists, they just don't like the look.

Peter,

I have friends that used them on Les Pauls. So far, I have not known anyone to use one on an acoustic. I agree with Mojo about having a quality luthier examine your guitar for other remedies first before going with the String Butler.

Thanks, Mojo & Lamar.
My curiosity is not borne of any major tuning issues - more about that "what's the best design/architecture" debate, and how the the strings pass through the nut:
straight or bent? Typically, the G-string can be the most common culprit. One idea was simply to use a little bit of dry lubricant to reduce any binding - rather that pay for and install that after-market product.
I wanted to read some first-hand opinions - yea or nay.
I appreciate yours; Cheers.

BUMP - here's a guitar with the headstock designed to fix the string-angle issue...
some fun pickin', too.

https://www.youtube.com/watch?v=5X7v7iSA4yY