It's a misconception to think of an open diff as only powering one side. No one directly said that here, but I know lots of folks think that from conversations I've had.
In an open diff, each side gets exactly the same amount of torque, no more or no less (not including a tiny fraction caused by the gearing geometry itself). Also, for a given input (drive-shaft) speed, the COMBINED speed of the two sides will be the same. So, during normal driving down the highway, both wheels are equally powered, at the same speed.
The problem is that since neither wheel can get MORE torque than the other, and since a free-spinning wheel can't accept any torque, the non-spinning wheel doesn't get any either. The free-spinner's speed just increases to twice the speed as would be if both could turn. With the LS, the spinning side uses some technique to grab onto the other side and pull it along, thus transferring EXTRA torque to the side that actually has more traction. For anyone that's into learning about stuff like this, the howstuffworks.com website has TONs of info.
I don't have any scientific testing evidence, but I would think that without an LS, if you could punch hard enough to break both wheels loose at the same time, they would both continue to spin. As one gets more traction than the other, it would start to slow down, speeding the other up. As long as the vehicle started moving enough while both were still spinning, you might be able to lay a good double patch. I'd suspect though that one stripe would be longer than the other.
I too am in the camp of "wish I had it", but I couldn't resist everything else about the 2011 I found on my dealer's lot, but it has the 3:55s. I'm not TOO worried about it though. My '98 didn't have it either, and I even plowed with that. The only real issues I had were when starting on wet or slippery pavement in 2WD. I figure all of the problem cases I had with the old one will be dealt with fine on the new one with the traction control.
For me, it's way better to have it, but certainly not a deal-killer.