I miss the times when playing Queen of Board was actually a fun for me. I just haven't got time back then and now I dont have the patience.
I miss people hosting hotels, mostly because there was a lot of idiots(mostly from poland) and you could have a lot of fun because of them. I also miss it because there were many people who played only because they wanted to talk with someone. You could just sit in a stupid hotel level to about 3 AM.
I miss cant werify, mega lagz, duel for JCS.
It's also possibile that I just miss times, when this game was more fun for me, when I was younger. It could be still a fun, but its not because everyone is obsessed with ladders etc. This game is more about some rankings, less about fun(I remember when I was playing a JDC duel with some guy. That duel was quite unusual because we played with really strange rules - who will fall out from the lake at hotel wolf.j2l will score for the opponent! I lost 5-3, bah. Then I won treasure JDC duel, because I had 140 diamonds and he had got 80, so we decided that I won 14-8).
I miss the times when most people got tricked by alt+f4 thing.
Somehow I miss the times when there was no plus or carrotade. Immortality after getting carrot, random seekholes, cheaters crawling around the servers, "pro" admins using Forest(or whatever was its name). For some reason it was fun.
I miss the times when people were hosting good tests mostly for 1.23 version. Now I can't even disable multiversion at 1.23 server because TSFers can join anyway.
I miss the times when I was dueling with my brother at splitscreen at bbswing probably.
I miss the times when "chat as" option at coolhax was actually working, lol.
I miss that amazement when I saw for the first time a coop server(probably NC one). I was asking everyone how is that possibile?
I miss nabs asking "how to fly with spaz", "how do you wallclimb with jazz", or entering server with nick like "HOWTOCHAT".

Now it's also a fun, but this game get a bit too "official" for me. You could be really happy before the "age of plus" when you saw a five jj2 servers at one time! That was amazing and insane! Now you are scared when Zeal servers are down and you have no idea what to do, so you can't do anything because it doesn't happen often that someone is hosting something nice. Maybe I was just a bit younger, and things that annoyed me back then now makes me laugh, and probably it makes me laugh because now this game is more stable.

... Whatever, it seems that I mostly miss the fun(of course its still fun to play it!) and randomness at this game. And its 3 AM here, not sure why the hell I'm not sleeping yet.