I have an S-Tec in my Cessna with Alt, GPSS etc and it has been faultless. I like the fact that it is separate from from the AI (which has failed more than once).
I also don't like the AI linked units after having a nasty experience mid channel in a Senecca in IMC when the AI failed and the auto pilot followed it to turn us upside down.
Its like everything in aviation, over priced and out of date technology!