NannyMae- that seat actually performs amazingly in all crash tests. It's crazy safe, better than a booster, a FF harness, it's awesome. Just like the laptop was awesome. It is NOT a shield booster in any way which I think is what you're clouding your mind with. A child would not likely be ejected in a rollover. It's possible, but it's highly unlikely. And I'd take that ever so slight (almost non-existent) chance in exchange for the awesome safety it offers all around.
I loved it, though the booster was highly unimpressive and it was HARD all over, even the headwings are hard plastic without even regular foam on them, just the cover. And the shield only goes to 40 pounds. But if they would pad those headwings and make the shield go higher, I'd own one in a heartbeat.