Centaur is way better than 105 and well up to what Ultegra is all about. I have been running a chorus 2000 10spd group since 2000 and yes it gets better and better. I recently replaced my 9spd ultegra group with Centaur ( which is identical to Chorus 2000 apart from carbon finish levers) and it runs great. I daresay that the 2006 105 10 spd group has ironed out all the ****e gremlins in the system such as non braking brakes and cheap feel and excess weight. I do think that the Ultegra 10sp is a lot lighter than Centaur and the cset/bb system is way ahead.