I have been playing on-and-off for about 3 years now. I started by playing a Mage right at the beginning of TBC expansion, but now I play a priest since the launch of Cataclysm.
I am mostly a raider, in a progression guild, we are 10/12 for the current Tier 11 content, working intently on Nefarian. Other than that, we have the other 10 bosses on an easy farm schedule each week. We haven't bothered with Al'akir at this point, because we feel downing Nefarian is much more important.
Yesterday while raiding, we got a couple of the boss achievements, they were kind of a surprise to most, because we weren't striving to get them at the time, they just happened.