Hi all. I purchased the ProQD i3 also and have dived about 10 times with it so far. Great BC, no complaints at all. It is quite slim and comfortable. Couple of interesting points.
I also have one of the Morphos Pro BCs from Mares that are designed specifically for travelling. They even come with their own "built in" football shaped bag that once turned inside out miraculously zips over the BC and makes it ready for packing. The i3 comes with none of that fancy-ness but packs flatter, lighter and easier than the Morphos anyway.
The Morphos has the Mares equivilent of the i3, they call it AirTrim. The Mares works ok but the buttons are not as intuitive as the i3 lever (simply lift up to go up, push down to go down) and the dumping of air is significantly slower also than the i3 which if you are playing with your boyancy a bit takes a bit of getting used to. Something I noticed about the Mares Air Trim system is that the dumping of air is not only slower, but quieter. Because you can't hear the air escaping or see the air escaping (in a traditional corrugated hose style you hold it up press the button, look up and watch the air escaping) you tend to over compensate and let too much air out. The i3 is a little easier, you hear the air going and gives some confidence that it is working from the moment you use it. I found it took me a few dives with the Mares before I started trusting it and having hassle free dives.
A note on the Octo-pocket. I think the designers had a great idea. Shame it doesn't really work unless the moon is full, you chant a secret incantation for 2 days before you dive and hold your mouth just right. I have an AquaLung legend Octo and the thing hardly ever stays in the pocket. Shore dives are 50:50. Boat dives, giant stride into the water, rapid exit of the octo from the pocket. Stick it on a clip like everyone else and be happy.
In summary, I love the i3. Super comfortable. I'm diving with a small steel tank, have no weight in the trim pockets and only 5 pound in each front weight pocket. Easy to get on and off without assistance, easy to stablise boyancy from the first dive I stuck it on. Would recomend it to anyone.
Cheers
Pete