Very, very worried. I'm trying not to be discouraged by thoughts of "They Changed It Now It Sucks" [http://tvtropes.org/pmwiki/pmwiki.php/Main/TheyChangedItNowItSucks] and I'm trying to keep an open mind, but the one thing I won't accept is if they remove the Skill Build system. I don't mind replacing the instances with open, shared worlds (although I love the instanced gameplay of the original), I'm concerned about the effects on balance that having multiple races will bring but am willing to give it a go, but if they replace the flawless system used in Guild Wars (choose only 8 skills from your primary and secondary class) then the game isn't Guild Wars any more. It was the most defining feature of the original and if they drop it then they can call the game whatever they like, set it in any fantasy realm they like, but it will NOT be Guild Wars any more.
Oh yeah, and from the sound of it, skill chains (on the Warrior page) are a DAFT idea. The listed example combo (Sever Artery, Gash, Final Thrust) worked perfectly well in GW on their own because each skill could be used in different combinations (I, for example, preferred to use Gash after Crippling Slash, not Sever Artery). It looks like a perfect example of the developers trying to fix what was never broken and possibly breaking it in the process.
I'm willing to give the game a go regardless because Guild Wars is my favourite MMO of all time (in fact, I just posted a thread about how it spoiled me for the entire genre [http://www.escapistmagazine.com/forums/read/9.205548-Has-a-game-ever-spoiled-you-for-a-genre]) and I have the greatest of respect for ArenaNet as developers. But I remain greatly concerned.