I use it as well. I've used in in my previous bike and I think it takes care of balancing without the need for weights. It also gives me a little bit of comfort as far as enhanced puncture protection.
I did not use it for the 908s because I never really thought about it. But when I changed tires the wheels were definitely out of balance (rough at slow speed) so I put it in and removed the weights. I think it works and will continue to use it.