I never enjoyed it, after an extremely demotivating Naxxramas, Ulduar started implementing a lot of the features I dislike in modern raiding, as in, the first steps towards "heroic" encounters. The instance itself had very cool encounters though. I just preferred when raiding used to be about a few easy bosses, some in between, a couple hard fights and lastly a very hard boss. Heroic modes and different difficulty tiers never really felt right to me (although I fully understand their necessity for MOST GAMERS, sadly I'm not part of that group)
The pinnacle of raiding to me was T5, there will never be fights like Kael/Vashj again - those for me are gaming art