I'm currently applying to Reclaimed, which is one of the more advanced guilds on Skywall, working on Sunwell at the moment. I thought it would be interesting to try a more hardcore approach to raiding for a while. I respecced back to Holy and am healing for the most part.
I haven't actually seen Sunwell yet, but I did get taken on a Black Temple run, which was pretty interesting. It's illuminating to see how this guild does stuff.
The biggest thing is that they are fast. They just move from trash pack to pack swiftly. People go afk, come back, the raid keeps going. Heck, the main tank went afk and the raid kept going, just using the other tanks. Even boss attempts are fast. Wipe, everyone release, run back in, buff and pull again. It seems like this guild gets in three attempts in the same time it would take the other guilds I've been in to do one attempt.
The pace is the hardest thing for me to get used to. I honestly couldn't tell you very much about the bosses in the first part of Black Temple, as it's kind of a blur.
All in all, it's been a pretty interesting experience so far. We'll see how things turn out.