I've used the SeaQuest ProQD with the i3 inflator for years now, nearly 200 dives on it.
I love it, but I can also see where it's not for everyone.
As far as a vest-style BCD (forget about the inflator for a moment - and the ProQD is also available without the i3), I think it's one of the better ones on the market. It does NOT "squeeze" when it inflates like some others do: it's designed to kind of open outward when inflated (think split lobster tail). It has decent-capacity trim pockets high enough to actually trim you out.
Just the right number of D-rings in just the right places, and the belt webbing can hold several accessory pouches for extra lenses, lights, etc. Even though it has those mounting points on the left pocket for a knife, I found that to be a hassle with my pony's reg hose routing and moved the knife down to the belt as well.
Single cam band, which some folks don't like (they prefer double). But it's a good lock against the ribbed, rigid plate in back. I also hang a pony mount off the band as well with no problem.
One recommendation if you're a spearo or photog like myself and spend some time inverted near the reef: rig up a crotch strap! Without it, the vest will ride up your shoulders when inverted. All vests do that without a strap. I was able to adapt the standard 2" Dive Rite strap quite easily to the ProQD.
Also, I recommend buying some larger vest pocket zipper pulls. The stock ones are hard to grab with gloves. OMS makes some nice big red pulls that work much better, you could always just make some as well.
Now regarding the i3 inflator: I can see where using it with a drysuit might be problematic. I'm strictly warm water, tho, so that's no issue for me. What I love about the inflator isn't really so much the inflator, it's the deflator. It opens both the shoulder and the rear valves at once, so you vent pretty much no matter what position you're in. Very nice. A buddy of mine dives the ProQD/i3 and doesn't even hook up the i3 inflator hose - but she uses it to deflate all the time. Reaching for it to inflate/deflate becomes second nature.
I use an AirSource 2 as my backup reg, so I can inflate using the more "standard" method if I want; that's a good option especially if you expect your buddy to be able to inflate or deflate your BC underwater, since they might not even think to look for the lever. I'm mostly solo so that's not much of a factor. Either way, there's a manual dump for the shoulder vent that's pretty standard.
In short, the ProQD is a very good recreational, warm-water jacket-style BC, and the i3 inflator is handy and intuitive, especially for deflation.
