Trio Pro Pilot
Rich,
We have one in our -6. With an external switch, we can drive it from our Apollo GX60 IFR GPS, or the Garmin 496. Either way, it works great, but especially with the GPSS commands from the GX60. We may have the only GX60 to ProPilot installation in the world, I don't know, but it is an excellent combination in my opinion. Of course GNS 430W's are a lot more common these days and if that's the way you want to go, check to see if Trio has the ARINC GPSS and GPSV functionality ready to ship yet.
Vertical speed, altitude capture, altitude hold all work like they are supposed to. Personally I wouldn't bother with the autotrim feature in a 2-seater RV, but it is available as an option.
One thing to keep in mind with the ProPilot, is that it is what the Trio guys call a "fully featured autopilot". It does a lot of things that might otherwise be done by other instruments... Displaying BTW, DTK, XTK, next waypoint identifier, ETE, rate of turn, fuel flow and mpg, etc., etc. Even if the functionality is duplicated elsewhere in your panel, redundancy can be a good thing.
--Paul