There was another thread recently where this was touched upon. I use them in my GXP and did in my SE as well. I find they burn out quite frequently. I've only had my GXP a little over a year and I'm on my third set. I tried the Ultra'* but didn't find a great deal of improvement. Most places here don't stock the Ultra'* anymore. The one nice thing is predictability. If one goes, you know the other isn't far behind.
A friend of mine with a VW has told me of similar experiences.
StingRay Bike w/cards in the spokes, Weeeeeee!