The items mentioned above go equally for the RV-9.
The installation, in particular the pitch servo, is best done when building but can be performed after the fact, as I did. I only say this because it requires the removal of the floor boards, working in the tail cone, and up under the panel is a pain. However, this is no different than installing any other autopilot and is not unique to Dynon. On the -9, installing the roll servo in the right wing is very easy at any time.
I highly recommend running the wires out to the right wing bell crank and back to the pitch bell crank behind the baggage compartment bulkhead and installing the pitch servo bracket during construction. More so if you think you might want an autopilot at some point in the future.
Total installed weight of two servos and the AP74 is less than five pounds, including the wiring. For those of us who are very concerned about weight, this is a very little penalty for the advantage of having a two axis autopilot.
Functionality of the Dynon autopilot is just outstanding and it is easy to learn and use.
Initially I flew the AP without the benefit of the AP74 and found it acceptable but the thing really shines when coupled with the AP74. The ability to dial in a heading, altitude, barometric pressure, etc. is well worth the minor additional cost of this unit.
In my installation, my sole means of navigation is a Garmin 496. The 496’s vertical navigation function is set to 500 FPM, as is the vertical navigation on the Dynon. The mix works out very nicely. When flying at altitude, the Garmin notifies the user when to begin the decent and a glide slope symbol is displayed on the left side of the artificial horizon. Just engage the desired altitude when the glide slope centers and the autopilot will fly you right down (or up) to the desired altitude. It will also fly any of the approaches in the 496 but you might have to manage the vertical navigation, still easy enough to do for this VFR pilot. (I am not encouraging anyone to fly IFR w/o the proper training and equipment but it is nice to know I can do it should I ever need to.)
The AP74 also has a 180 emergency about face button. (This also availble through the D10A/D100/D180 menu buttons.) This is a great feature for VFR pilots who blunder into a cloud, all they have to do is hit the button and the AP will get them back into the clear air they just left behind.
The screen interface is also very easy to use and understand. No one should have any issues learning how to use this autopilot. In particular, I like the trim indicator. This helps the autopilot fly the airplane as it tells the human pilot when to trim up or down, thus reducing drag.
Dynon has done a great job merging the EFIS and the autopilot into a simple, easy to use, intuitive, integrated system.