I've been using these for about 3 maybe 4 years now.
It's a great, great cleaner. I've used it on all my guitars, the bottle lasts forever if you don't over use it. Which is always a big plus.
It leaves no marks. Keep in mind that it's a guitar CLEANER & POLISH. Meaning once you wipe your guitar once, turn the cloth to a dry side and buff it out.
It brings shine back to your instrument, removes grime, sweat and dust. And also using it on the guitar of a neck that is high gloss is a dream. You get such a smooth feeling neck afterwards it's a dream to have!
I fully recommend this, use it as described on the bottle and get your instrument clean!