Melanie, my first BCD was an AL Pro QD with an i3 system... from 10 years ago. I used it for years and the system is pretty slick. When I became an instructor, I switched to a traditional inflator because that's what my students use. In fact, I attached a traditional inflator to my Pro QD... so I still had the i3 lever, but used the traditional inflator.
I used just the traditional inflator to inflate, but the i3 lever could still be used to deflate. It's very nice in that respect because pushing down on the lever opens the top and bottom dump valves.
I have had no problems personally with my i3, and after 10 years it still functions just fine.
However... my mother bought an AL Lotus BCD with the i3 six years ago. Last year she had a problem with the i3 system, it wouldn't deflate properly. She took it to the local dive shop and they sent it to Aqualung (fortunately we live not far from AL headquarters... the shop may have just dropped it off, no shipping involved.)
The AL people reported back that the i3 system was not repairable, and they wanted to "destroy" the BCD. They recommended my mom just buy a new BCD. I intervened, insisted that they send it back.
Basically what had happened with my mom's i3 system was the little cables that open the dump valves have some plastic parts in them. A couple of these crucial plastic parts had been bent. And according to AL, there was no practical way to open the system and replace the parts.
So I put a standard inflator on my mom's BCD and I added pulls to the dump valves so she could operate them manually. In essence, I bypassed the i3 system and converted the BCD to a traditional system. And it still works great.
In summary, my opinion of the i3:
Pros: nice little system, very intuitive and easy to operate; if necessary, you can convert to a traditional inflate/deflate system
Cons: non-traditional, so it might confuse others; if you have a problem with it, don't expect AL to fix it