I've got the No-Slip in the rear of my 5-speed manual. And, yep, the body roll is the first thing I noticed when I picked it up from the shop.
For instance, at a stop light, when the light turns green, and I put it in gear and give it throttle, the whole jeep torques slightly to one side (more so than normal). But it's not always to the same side. Sometimes it rolls to the left, sometimes to the right, and sometimes not at all. And it's obviously more pronounced with the sway bar disconnected.
It must have something to do with the way the locker engages the pinion/drivetrain. If someone has a good explanation as to what causes it, I'm all ears.
It also occasionally unloads strain on the drivetrain at odd moments, causing a snap or bang from the rear that you mentioned. But I'm told this is normal behavior from any locker. In high-traction situations (like on asphalt), when the tires need to turn at different rates, and can't because the No-Slip has not disengaged, something has to give.
So, in short, it's normal behavior, and nothing to really worry about.
However, I'll be waiting for your post after your first experience in the snow with a No-Slip.