I have the Alpha Systems Eagle Dual kit and have been very happy with it. I like the military-style display (I'm used to it). I also like the fact that for my A36 it is calibrated for flaps and gear up, flaps approach and for flaps and gear down (different calibrations). Having said that, it is NOT a military-grade system. It is accurate, but does not have the fine resolution of a military vane or servo system. Think of it as taking a measurement with a calibrated ruler which is marked only every inch - you have to do some guessing in between. In practice, I use it to set the AoA in the pattern and cross check it with airspeed, then transition to airspeed with AoA cross check on about 1/2-mile final.
Hi Jon, I have a Garmin AoA system/indicator installed and I'd recommend it. The system seems to work well and the indicator is easy to see/read on the glareshield in day or night conditions. Interestingly, I find I use it some while on final for landing but I especially like to scan it during the turn to base and final to ensure I'm not pushing it too hard and getting too slow. I think of it as another tool to catch and warn me of an impending situation due to a lack of technique or distraction. Hope that helps.