The Steinberger Gearless tuners are probably more suited for Gibson Firebird style of headstock. I would prefer tuning keys with pegs for regular 6-in-line Fender style or 3 x 3 Gibson style headstocks.
I have installed one set and they are quite easy to mount so long as you read the instructions a few times over. The keyhole size is 13/32" or 10mm as with Schallers.
Application-wise, there are good and bad reports.
Firstly, they are quite heavy and if you have a hollow body guitar which there may be a problem with neck heavy issues, these tuners will really tip the balance.
Some complained that the B and Hi-E strings tend to break more readily than normal tuners as the grooves where the strings pass tend to wear at the contact point.
As for tuning stability, they appear to be quite good.
They enable straight string pull and there is no need to have string trees or retainers.