FWIW, I've got no complaints with the performance of the old Beergun. I've never had the tip fall off, the carbonation is perfect, and I feel confident that the co2 flushing is adequate for long-term storage. I had tried the BM version but always made a huge mess and wasted a ton of beer. I know others have had better results, so its probably user error, but the mess is minimal with the Blichman.
The only thing that I find annoying is that its a bit of a hassle. You've got to flush it with sanitizer, disconnect the liquid keg line and connect your beergun, connect it to the co2, use it, clean it, then clean up whatever mess I made. My kegerator is a tight squeeze and my CO2 lines go through it, so I've got lines everywhere and they always seem just short enough, or restricted enough, that its a bit more annoying than it should be.
Its great when I have to fill 20 bottles or if I'm entering a competition and don't mind the extra time and effort to get it right. But if I'm on my way out the door and think "oh, I should bring a growler" or I'm trying to pack up the car after work and get on the road for trip, or even just trying to get the damn kids out the door on time, taking 20-30 min to fill up a growler isn't usually worth it.
As an aside, I just bought a growler filler from Midwest that is just a silicone tube with a connection that fits into a perlick faucet. I'm not worried about co2 flushing a growler because its not intended to last more than a day or two. As long as the carbonation is okay, I'll be thrilled. In fact, I'd probably use it for bottles too, relegating the beergun to competition bottles only.