Since killing LK a couple of weeks back, I've been working my way through the heroic modes in ICC10. Currently I've beaten the first six bosses, and I must say it really adds a great deal of excitement to the encounters. In fact, some of the encounters feel like the heroic mode is the "proper" version of the fight - particularly Rotface and Festergut where the heroic modes have some extra voice acting, and new features which are implemented in an amusing way.
I think that LK heroic might be beyond us given the extreme difficulty of the fight (I think only one guild on my server has beaten it so far), but we will certainly try to get the Glory of the Icecrown Raider achievement, which has a special dragon mount as a reward.
The major roadblocks are likely to be Sindragosa heroic and the Sindragosa achievement, both of which look like an absolute swine, but we managed to get one of the harder achievements last night - Nausea, Heartburn, Indigestion.
This requires you to complete the encounter without using the abomination's slow ability on the various oozes and clouds which spawn during the fight. What this means is that you are going to get hit by the adds. A lot.
Positioning is vital. When the green oozes spawn then you need to remember that the AoE damage when it reaches its target is split between all players in range. We split the raid into two groups for the oozes - the melee dps and tank in one position, and the ranged dps and healers in another (we used two healers). We normally killed the green ooze before it exploded for the second time, meaning that raid damage was manageable. The orange oozes are tougher, and you need to remember that damage from these mobs is not split between nearby players - thus you need to be spread out when these spawn. You also need to be aware of the DoT effect on the person that the orange ooze is targeting - that person will need quite a lot of healing while the ooze chases them. We used heroism in phase 2 to get the oozes out of the way as quickly as possible, and once you get into phase 3 it's the same as normal (except you won't have heroism available, so your execution needs to be better).
It's really quite fun, and makes the old, familiar fight a lot more interesting.