I bought one and compared it to a friend of mine who recommended it. I didn't like the inconsistency with the comparison unit on the same jump (I compared it to another Neptune on about 4 jumps). I wanted it to replace my wrist altimeter, and the altitude readout functions seemed OK. My primary interest was in FF speeds / fall rate... it wasn't consistent. We ended up with different speeds of freefall on the same jump. The differences were at times as much as 10 mph at the same altitude, and we were both in the same formation. The overall average speeds were comperable, but only after I used the unit for a few jumps (as if it had to "set itself" by being used. The unit came with two batteries, and in two days, both batteries were showing half charge. Total FF time wasn't consistent with my Pro-Track in my helmet, which may be explained by it's being in my helmet vs. on my wrist. On one jump it was within a second of my Pro-Track; on another there was an 8 second disparity.