There are few things I actively dislike about Guild Wars. Mostly I just lack new gameplay elements.

The one thing I actively dislike are healer monks. As it stands, monks are a prominent class, masters of denial and delaying the outcome of battles. Protection - okay, smiting - okay, healing - not okay. All classes have unique healing skills of their own, and I would have preferred if there was no healing class, but the amount of healing skills assigned more uniformly among the classes. Monks must die!.. eh...

The other thing I actively disliked was the unlocking of skills. My faith in ArenaNet wavered as I was afraid they would mess it up. It turned out to be okay, though.

ArenaNet manages to surprise me because they actually listen to players. Every time I log on to Guild Wars, there are changes to the better. Even if the changes are small, they are to the point - exactly what was needed.

That said, let's see what I find lacking after the first chapter of Guild Wars.

More PvP options.

For a game designed primarily for PvP, there aren't many options. Random 4v4 is fun, but it does not give fame. As for the tournament, it takes too long to assemble a halfway decent team, and I'm not willing to spend most of my time networking outside the game when all I want is to play it.

More PvE endgame options.

PvE has to be competitive as well, even if it is only economic, status based, or ladder. There should be more ways to show status other than having ascended armor.

More options to manage relationships.

I find it hard to find people who are skillful and fun to play with. Of the few, most are guilded. It would be interesting to explore other, additonal ways to manage relationships. (Not just having a guild member list and a friend list, but something between. Perhaps a trust-based circle, with the ability to group tell the members of the circle, two or three connections deep.)

Persistence.

I don't know if semi-persistent (district based) hunting grounds can be implemented, but it would be nice. District based is still much better than having separate shards.

It could make groups form more naturally, and make finding out which people to befriend (or guild) more easily. It could be helpful for both endgame PvE (possibly more status options) and PvP (easier to build a good guild).

Of course, traditional persistence is the first thing that was sacrificed in Guild Wars, but it would be interesting to see how it could be integrated back again.

Free trial.

I'm surprised there isn't one already. For roleplay characters allow access only to the tutorial region, for PvP characters allow only preconstructed builds, and you're good to go.

I eagerly await the upcoming Guild Wars chapters!