I changed my cassette and Ultegra derailler to a Mtn bike cassette. The difference is amazing, but I lost my higher end derailler. The gear shifting is not as smooth as with the Ultegra, they changed my chain and it works like a charm. I would seriously consider changing if you do steep climbs. The LBS told me that some of his customers go to France to try the Tour the France route and they change their deraillers and cassettes, because the mountains are so steep, they could never do it with their regular gears and they have the high end bikes.