I purchased an unused used unit for less than a hundred dollars. The cadence magnet was missing and the speed magnet did not fit my spokes. However it was not a problem since it works fine with the existing magnets I was using for my Astrale 8.
It was easy to install and I found the instructions written well enough to understand with very little problem. So far I have had a very good experience. As soon as I wake up the unit it picks up heart rate immediately and the auto function works well. Wandering away from the bike at rest stops has not been problematic either. If it has been less than 5 minutes it picks up heart rate right away and if wakeup is needed a touch of the button is all it takes.
There were 5 segments on the 160-mile RAIN so I used the lap function to record data which I found informative. Two Garmin units measured the distance at 160 and 159.8 respectively while the Cateye measure at 160.35 which is a 2/10's of one percent error rate. I think 2-3% is acceptable so the Cateye is outstanding. A lot more data is nice but the amount the V3 supplies is plenty for me. I record data in a spreadsheet so the lack of a download feature does not bother me. My experience has only been a couple of weeks so hopefully the long term quality that most Cateye computers have exhibited is in this unit.
EDIT: We were behind the start line when we began riding and I had the unit start measuring then. There was too much congestion and I did not want to be distracted resetting the unit as we crossed the start line so the unit total distance measurement is even more accurate than I indicated.