I actually had the official Apple Smart Battery case for awhile, but ended up returning it. I really liked the fact that it used a Lightning port as you mentioned. And I actually liked the "hump" on the back as I thought it made the phone easier to hold.
However, what I couldn't get over was the added weight. It just seemed to weigh down my pocket too much. So I'm back to carrying my phone in one pocket and an Anker power bank in the other.
I agree with you @demol3: I would like to see wider adoption of the Lightning port on battery cases (and power banks)!