I have used a Chrony since the early 90's. They are cheap, and reliable.
I have experienced a few small problems. But I definitely would still recomend them.
As far as accuracy goes, if in doubt, run a few 22lr's through it to confirm velocity levels.
The 22lr is a really good yardstick, so to speak.
I have used my chrony to get 8 or 9 different rifles of mine tuned and consistantly accurate to 1000yds. I have also used the chrony data to get me to 1900 yds.
I think I would have had trouble getting my rifles on target at those distances if my Chrony wasnt "very" close to the correct velocities.
I am sure that most chronygraph brands are just fine. And you dont have to break the bank to get good/accurate readings.
Good luck and have fun with it!