I haven't, but it seems to be getting very good reviews. A grow pal bought one and should be receiving it in about 15 days so we will compare it with my Apogee SQ520. For the price, and if it really is as accurate, It is a really good buy considering also the small features it has.... my apogee came in a bag in bubble wrap and that's it!... at least a cardboard box would have been appreciated.