I just spent my first longer trip with the dragonfly airtrim, and it worked fine. Some nit-picky things: it doesn't like to drain the last bits of rinse water very easily. You need to work the water around to where it can drain. But, on the flip side, it is very easy to rinse the inside by unscrewing the upper manual exhaust valve cover. This is much better than having to put water through the inflator hose mouthpiece. The other thing that isn't so great, but which isn't a big deal with a buddy, is that the shoulder straps twist pretty easily, often twisting a couple of turns. Also, contrary to the advertising, you do need to be a bit cognizent of body positioning to exhaust air from the thing, especially when you're in the "normal" slightly head-up stomach down position and most of the air is in the wings -- in this position, some air trapping occurs. Still, you get used to it. And finally, it's impossible to see that you're actually venting air when you can't see the bubbles coming out. In most cases, you can feel the venting bubbles, but when you've only got a bit left to vent and run into the aforementioned problems with venting positioning, it's a bit more difficult to tell what's going on.
But all that said, I do like it. The airtrim is particularly useful because it's in a fixed place that's easy to find, instead of having to grab around for a wayward inflator hose, and for me, it makes things tidy during ascent too, when you're holding you computer to manage your ascent rate.
-Simon
