I got a set of these to go on a Peavey SC-2 which I'm using as a platform for upgrading. They fit the existing holes very well and were really straightforward to fit. I put them on at the same time as a String Butler (the V3 model) and didn't have any problems fitting both together.
Installing new strings was really easy and quick. I didn't wrap the strings round the posts at all, just threaded them through the post, tightened the locking screw on the back, trimmed the ends off and tuned up. I was a bit nervous about whether this would hold the strings tightly enough, especially after cutting the ends down so short. Have to say, they're holding absolutely fine.
Tuning stability is really good with these on. You'll need to allow strings to stretch for a couple of days but then they seem to hold tuning really well.
The only word of caution I have is that the black coating can be easy to scratch when you're installing the machine heads. What I found helped was using one of those spanners that fits over the nut completely (the sort that comes in Ikea kits).
Very happy with these machine heads. They feel like they're really good quality. They're not exactly stiff to tune but they don't have that loose feeling of the old tuners I had on the guitar.
