My wife and I also have the Atomic B2 & SSI combo. We also have the Vytec computers with the wireless connection, so we have two less hoses than most people.
We've had these for nearly two years and have over 100 dives on them. We bought them shortly after our OW certification so we are very comfortable using them, but have not used the normal console & alternate air source much, so me comparing the two sets of equipment is not fair to the "normal" way.
ScarefaceDM brings up a good point about dumping air on an ascent, but my wife & I make it a point to practice our safety skills often so we don't have an issue in an out of air situation (or other equipment failure).
That said, you have to do things a little differently with an SS1 than others because the BCD inflator is on the same hose.
One key thing for us is that my wife is ALWAYS my buddy, and we know each other's equipment well.
When we have taken classes and been buddied up with strangers we always have to explain in detail how to handle an out of air situation. While most of us are taught to hand over our alternate to the person out of air, I think in the real world they are going to take the primary anyhow, and I'll be breathing on my alternate, and this is exactly how the SS1 is meant to be used.
The only difference is how to handle venting the air in the BCD as you surface, and you need to know how to do this, and practice it.
It is different, but not that much harder to control your buoyancy using the SS1 as opposed to the conventional way.
However, I would NOT recommend anyone to get an SS1 unless you practice regularly on how to use your equipment. When you are in a real emergency it is not the time to try to figure out how to use the equipment. Breathing on the SS1 in an out of air situation is easy. Ascending safetly and under control is harder. If you don't practice it you could find yourself in an uncontrolled ascent for the both of you, which could result in DCS.
By the way, as part of the practice we breathe off our SS1's at least once during every dive day. They breathe great, even at depth.
Wally