In Alt in original Hewland engined form they only had 75hp which didn't really cut it. The original (2-stroke) engine suffered from lubrication problems due to an inherent fault. By the time the problem was solved the ARV's reputation had suffered badly.
All the ones still flying with a Hewland should be OK now as long as the mods were incorporated. One which suffered a snapped crankshaft has been re-engined with a Rotax 914S (I think it's an S) but I read in Pilot that this involved putting a lead weight in the tail to bring the C of G back within limits which didn't do the load lifting ability any good. At least one other has been re-engined with a Mid-West rotary which seemed to be a good option.
Cons
a) The Hewland engined ones did run out of puff on a hot day.
b) The nose wheel arrangement looks a tad ungainly
c) The steps into the cockpit were a bit fragile for the training environment
d) No heater (unforgiveable with a liquid cooled engine)
e) Limited seat adjustment
f) Hand brake rather than toe brakes (not as bad as it sounds as the handle was set below the throttle and was easy to use)
g) Minimal baggage storage
Pros
a) Fantastic handling and general 'chuckability'
b) Fantastic visibility
c) Stick not yoke
d) Quadrant throttle not Cessna type push-pull
e) Excellent panel layout, everything falls readily to hand
f) Positive ground handling
Overall they are great fun to fly and I have occasionally been tempted to get one myself, preferably one on a PFA Permit rather than a C of A.