Sorry, totally forgot to answer to this!
I tried voice activated (in fact, that's the default, I think), but it was so incredibly sensible that I was always on and driving you guys crazy

(not helped by the fact I had a fan on at the time... you know, Madrid summer + no air conditioning :S).
The thing is that I couldn't find a slider to set the voice activation level so that it wasn't on all the time, so I just switched to push-to-talk so that you guys wouldn't have to kill me.

I'll try to mess around with Mumble again when I have the time.
If you want to take part in any kind of team-based competition - and that is what PvP is supposed to be in most MMOs (or most games involving teams playing versus teams for that matter) - you will reach a point where you absolutely need at least some kind of structure or organization. And yes, agreeing on a certain roster of classes/professions can be a part of that. After all, you probably won't win any match with 5 characters of the same class.
But sPvP isn't the problem at all. If they want to enforce roles/classes in their sPvP team, good for them (that's probably a must, in fact). The problem is that these guys (or at least some members) actively tried to prevent others from playing WvW; in other words, they literally wanted to monopolize it, to the detriment of anyone else in their server. That's actually a step further than militaristic.
To be fair, the guys that made such statements were supposedly expelled from the guild, but both their actions to prevent that as it was happening (read: none) and their dialogue on other matters (the infamous "groupie" quote) seems to imply they're not exactly people normal guys would get along with well.
Guys, I already bought the game a long time ago. But only managed to play on one of the weekend betas sadly. I feel so left out now. t_t I mean I don't even know where to start. haha I've been reading some of the posts in here and I just don't get most of them (maybe you guys are just hardcore players?

).
OK, there's several factors here:
1) Most if not all of us are probably hardcore MMO players. I don't know if you have a background with MMOs, but if you don't, even the common terminology is certainly encyclopaedic and more than intimidating at first. When I started dating my current GF 6 years back, whenever I talked about WoW with a friend, for her, I could as well be speaking in another language.

2) Even for those with extensive MMO knowledge, GW2 is quite different and introduces quite a lot of new concepts and terminology that they might feel lost too.
3) I understand this is all quite a lot to take in and extremely intimidating, but remember the
Hitchhiker's Guide's maximum.
4) This is probably a really good start if you have the time and disposition:
http://www.gafguild.com/index.php?threads/guild-wars-2-mass-info-for-the-uninitiated-read-me.16/
5) If you still have any questions, shoot away!
Right, the question I wanted to make is: When it launches I just choose the server that the GAF guild is in?
Well, if you want. Nobody is forcing you, and you can do everything with everyone (since the game allows you to visit other people's servers, and play as if it was your own) except for WvW.
Can i change it afterwards?
You can guest (visit other people's servers) which is more than enough for anything (PvE, dungeons, PvP) except for WvW, since you're representing your home server. You can also move to a different server for a price that depends on the population of the server. ALL of your characters are transferred there, because all of them are in the same server.
And is there some sort of wiki for me to read to catch up on the news about the game changes, new races, etc?
There's a comprehensive wiki here:
http://wiki.guildwars2.com/wiki/Main_Page
As for "changes", I suspect you mean from Guild Wars? You're better off forgetting all you know about GW1 except for a few things like the limited ability pallette, the setting and the lore; GW2 is an extremely different game.