The downside to being the equivalent of a WoW immortal, having played close to non stop for the entire history of the game, is that you see a lot of things come and go. Guilds, players, friends, raids, dungeons, zones, expansions. It was all new once, and it all eventually isn't new anymore. And as a result, although I have in the past waged wars of words against nostalgia among the WoW playerbase, I can be as guilty of it as anyone.
There are, indeed, a great many things I miss. Some of them I get to see whenever I want, like Blackwing Lair and Un'Goro Crater, others are players who stopped playing, playstyles that are no longer valid (I loved and will always fondly remember the days of fury tanking Stratholme for my guild Eldritch Way over on Kilrogg, then taking the technique into raiding on Azjol-Nerub with Sworn, fury tanking in MC, BWL and AQ before finally speccing prot to tank Naxx) and even places that are just plain gone now. The other day, while doing my weekly scouring of the Barrens I realized that ever since Cataclysm, the zone I remember is gone, baby - Mankrik's wife is buried, and the days where I rolled a horde and leveled it to 60 just so I could attack my own guildmates when they raided the Crossroads are just as buried as she is.