For the most part, it's been pretty great, but one aspect of it is that with two hours a night, three nights a week, it can be a challenge to get through the farm content fast enough to get to the new bosses, especially once most of an instance is farm content. Even when you know all the fights and can burn through them, five bosses can take a lot of time to get knocked out in order to get face time on a new boss.
One of the innovations of Wrath of the Lich King was extending raid lockouts. What this allows you to do is to skip the bosses you already have on farm by, in effect, picking up where your last raid left off. Cleared everything but Nef last week and needing to work on the new encounter? Now you can just start up with everything you killed last week still dead. What could be the problem, you ask?