A great change in my opinion. Death Knight talents were sure getting confusing, especially in comparison to the other classes. I'm glad Blizzard acknowledges the fact that their generosity in allowing players to be versatile, ended up making talent trees filled with talents that are doing three different things each. Yes, Death Knight tanks may feel like they become homogenized and yes, Blood Dps (such as me) may feel facerolled, but in the end i am sure it will work out just fine. Mages have to live with the fact that Frost is (not yet) a valiable raid specc, even though there are probably a lot of Mages who would love to toss some Frostbolts at the boss' face like in the old days. Same will go for Blood when Cataclysm launches.
I believe that classes are not being homogenized, especially with the introduction of Mastery. And if you'd still have the feeling that guildie's Death Knight seems a lot like your own Death Knight, then there is Path of the Titans. Sure, some classes share similar abilities but that's to improve playing convenience. I really would QQ seeing more encounters like Instructor Razuvious introduced, where your raid is dependant of the ability of one single class.
Plus, Blizzard hasn't released it's topic about Death Knight changes yet. Who knows what it brings =)