No one ever likes changes to UI on sites they use. (See: The Humane Interface for detailed discussion.)
I will say I don't have speed issues, but it's obvious the SBN is juicing up the ability of their sub-sites to drive revenue. Hey do you think they bought CB for charity? Markos might play a loony lefty at DailyKos, but the guy is a shrew businessman.
To me the forums have remained unchanged which is cool. I always have felt that's the core of the CB community. I see the front page as the top of that community, with social integration, etc driving further community growth, and that's a good thing.
Integrating the commenting on articles versus forums is actually a hard problem and parallels an issue at my current job. I used to think it should flow through, but now I like it separate.
Anyways the community >> the interface, so I'll be staying.