I have been using them for about 8 years now and they are exceptionally reliable. They make string changes a matter of very few minutes instead of a forty days and forty nights ordeal.
I had one hiccup with one of the tuners a couple of years ago, but Grover customer service proved to be one of the best I have come across, ever, and the issue was sorted quickly and at no cost.
They are a bit on the taller side due to the type of the automatic locking mechanism, but I didn't find that to be an issue on a Les Paul.
I have had great experience both with the tuners and the Grover customer care.