I have a set of these on one of my bikes as well and have ridden them on my main bike for 2 years without any real problems (some small racing as well). I wouldn't use these for serious racing but only for one reason which is that you can ONLY use conical bottles in them. The definition of racing varies in here but if you do regular and long road races where you sometimes can get in a position where it's hard to get a bottle from your own team think of how annoying it would be if got a bottle from another team or neutral support and it wouldn't fit in your cage on a real hot day! I think that's also the reason those Elite cages for smaller bottles never caught on, not even with the big pro teams. We got those as well many years ago but never used them as they were utterly impractical in races.
If you on the other hand ride criteriums or local circuit races I don't see any real problem in using them to be honest. You usually don't grab any bottles there anyway (if it's even allowed) and on the rare days where you would you'd get your own anyway. Although there might be better cages available I never had any real problems with them and can't remember ever having lost a bottle out of them. For the ease of use, as Pritchet and Danton prove it's really personal if you'd like these or not.
Pez, I had the same problem you state once as well. It was during a race and on a frame and cage combo that must have weighed close to 12 lbs
Really annoying but I think it has more to do with either improper installation (I use locktite on those bolts now) or just bad luck somehow then with the cage you use. Riding a Colnago as a main bike I know my fair share of loose bottle cage inserts but I can't say I notice a difference after I started to use the BTP cages, they still need tightening every now and then (maybe every 10-15k km's?) but not more or less then with the cages I used before.