We have run them on a few Lvl 1 and 2 IPSC matches, Visibility in bright sunlight is not the best but can of course be overcome with some kind of sunshade. Battery life is great, after the initial sync I put them in flight mode though and I normally see devices returned with 80% charge after a 6 stage match.
Remember to switch them on and allow them to do any updates before the match so they dont start doing this when you start them up at the sync. If I can find a portable printer to use for verification purpose then I think we will have a fairly solid electronic scoring system.