Well, I was a heavy player of d2 for years, it would always draw me back at some point.
Until I saw guildwars, now I don't see any turning back, the game is really NOTHING like d2 in my opinion, superbly better graphics, more indepth, you don't have to grind for levels, do you remember hitting level 90 on d2? After that it was like omg, how much until next level?
You really don't have any item that I would consider "godly" which I think throws off a lot of people, this game to me is about your skill not how much you can attain as far as items would go but we will have to wait and see what is ahead of us in the next chapter in '06.
Another nice thing is you have no worries about "pk" players hostiling you while out on your adventure, however you may find yourself wishing you could hostile some of your team mates once in a while for pulling a "Leroy"
The game shouldn't be but has also become about "bling bling", which I have to admit my mesmer looks totally awesome in her 15k noble armor, it is no better than armor costing a fraction of the amount I paid, but I also know what it took for me to get her there and that is the reward that I gave her/myself for the accomplishment.
Support... I can't tell you how much it is appreciated. When was the last time you saw a rep from a company come into common town area and say hi, even ask about suggestions or troubles or be there for the launch of a contest the way she did with the gvg tournament recently.
Biggest favor you can do is with your first character, play the game through, follow each mission and don't get ran places right off otherwise you stand to miss a lot of the storyline. Save the running for the first time you meet a group of charr, you will understand this soon enough.
But by all means, have fun!
Welcome to the world of Tyria and welcome to Guildwars
