I can honestly say I'm glad I quit before Wrath of the Lich King. Pre-BC I was just raiding Molten Core, with some BWL and Ony thrown in. Nothing too fancy. I got into the hardcore raiding scene once TBC came out. I raided with a high end guild for a long time. It was great for a good while. Tier 5 content was actually quite hard. Taking down Lady Vashj, Kael. It was all great. Tier 6 was comparatively easy after looking back at Tier 5, but it was still fun. So I sat there in Tier 6 gear, I was proud of that of course. Granted on our server there were several other high end guilds around the same level as we were.
Oh then they nerfed everything. Vashj got nerfed, Kael got Nerfed, Sharaz got nerfed, Archimonde got nerfed, so did Illidan. All the harder fights were nerfed to the point where they were trivial. Then you had these upstart Tier 6 guilds essentially taking away what you worked so hard for. By the time Sunwell came out a vast majority of our guild has quit. Many came back to do Sunwell but the old feeling just wasn't there. Hurray we got Sunwell gear. Our guild didn't down Kil'Jaeden, our guild effectively split up and our members got diluted into other guilds.
Now at first when I skipped on Wrath I wasn't sure I had made the right choice, that is until I heard the 25th of November guild cleared what Wrath had to offer so far. They did this in what? 74 hours? That includes leveling to 80, prepairing for entry level raiding, and clearing 3 instances. Even when you consider their experience during beta, they still didn't have access to all the bosses, it's nuts. I was also generally opposed to the direction Blizzard was going with PvE class balance. They just wanted to give everything to everyone, and as a result the pure DPS classes got the shaft.
Anyways, World of WarCraft is now more about gear then anything else. Blizzard caters to those who don't give a shit about the experience and want shiny gear. Gone are the days of the gear people wore actually meaning something. I for one am glad I'm not playing WoW anymore. If I was ever to return to WoW it'd be on a casual basis. Endgame content just isn't worth it anymore.