I guess I'm not a casual player any more. My level 60 warrior and priest were in a casual guild, which was allied with a raiding guild, so I was participating in raids with that raiding guild. Now this alliance split up, and I left the casual guild to join the raiding guild. Staying with the casuals would have meant no more raiding, and I didn't want to lose that aspect of the game.
The problem with casual guilds is that they are so much less well organized than raiding guilds. Raiding guilds have a regular raid schedule, with systems on who gets a spot on the raid, and how loot is distributed. Casual guilds in most cases just have a forum and a guild chat. There are very few casual guilds having a calendar to organize 5-man instances or other non-raid events. Standing around stupidly and looking for a group is my least favorite part of WoW, events organized for a fixed time and place are much more my thing. So now I'm a raider, who would have thought that?
Actually I think I'm still more interested in 5-man casual content, it is just that I have run out of it with my level 60 characters. I've visited the level 60 5-man instances often enough to have all the gear I want from there and know the places inside out. And what else is there to do for a level 60 character? Grinding some faction really isn't my cup of tea. So the choice I had with my level 60s was basically retire or raid. I *was* thinking of the retiring option, only playing lower levels, but I'm looking forward to playing the Burning Crusade in 4 months or so. If I retire the level 60s now, I will have lost the social network needed to enjoy the level 61-70 content later this year. So I'm planning on going back to my previous schedule of raiding with my level 60 on the weekends, and playing the lower levels during the week. We'll see how that works out.