Patch 2.4 is removing the attunements to Mount Hyjal and the Black Temple. If you look at the WoW Dungeons and Raid forums, you'll see a lot of angst over this decision. First off, I fully support removing the attunements. In general, I think raid attunements beyond the first level are pointless and end up hurting the slower, less hardcore guilds.
However, the raiders complaining about the attunement removal do have a point, and it's worth considering their perspective. In my view, the issue is not really the attunements themselves, but rather the nature of the bosses right after the attunement.
Remember that for raiders, quality of reward needs to match the challenge overcome. However, it is generally accepted that the first few bosses of T6 content are "easy" and really are not worthy of the quality of loot that they drop. But this is acceptable because Kael and Vashj are so difficult. Early T6 bosses do not just reward you for beating the T6 boss, they also reward you for killing Kael/Vashj.
Essentially, the first few T6 bosses are "reward bosses". There are other reward bosses in the game: Void Reaver in Tempest Keep, the Chess event in Karazhan, the drakes in Blackwing Lair.
But with the attunement removal, you don't need to kill Kael/Vashj, so the challenge ceases to match the reward, and thus there's a lot of complaining. People are allowed to skip the hard content and access the easy bosses with over-generous rewards.
This happens on a lesser level with Void Reaver in Tempest Keep. Originally, you had to beat Magtheridon to get access to Void Reaver, and thus Void Reaver was essentially an extra reward for beating Magtheridon. But now you can go straight to Void Reaver, making his reward (T5 shoulders) greater than his challenge.
Another way to think about it is to look at the Chess event in Karazhan. There is no question that the Chess rewards seriously outstrip the challenge of that event. However, those epics are not just a reward for Chess, they're also a reward for getting that deep into Karazhan. If the Chess event came at the beginning of the instance, or after Attumen the Huntsman, it would make no sense. The reward would be disproportionate to the challenge on every level.
If the first boss in T6 content was the equivalent difficulty step of Razorgore in Blackwing Lair, there would be no complaints about removing attunements. Challenge would match reward, and everything would be fine with the world.
In general, I think that "reward bosses" are a bad idea. They encourage guilds to take shortcuts, to waste time and skip over content that would teach them necessary skills. I honestly believe that having guilds skip Magtheridon to go for Void Reaver has hurt them in the long run. Magtheridon teaches coordination skills that are very valuable in later T5 content.
Reward bosses are an especially bad idea to have near the beginning of an instance. If you have to have a reward boss, it is best to follow the Karazhan model, and drop it deep in the heart of the instance.