I have about 100 miles on a just installed Chorus 11-25 11-speed cassette. So far the shifting is excellent, noticeably improved over the Chorus 10 cassette. It seems to work just fine with a Record 10 rear derailler. Beware when installing it on any other hub than a Record hub as the hub may require a modification (Zipp, Rolf, are two I know of). The cassette does come with a variable assortment of spacers requiring more care during install. The smallest cog does just barely grab the end of the freehub, but seems solid when locked down with the lockring. It just looks odd though.