"Selling gameplay advantage for money," seems to be a popular topic right now, so allow me to talk about that a little. As many people on the forums have commented, Mercenary Heroes are, by and large, a cosmetic feature. There's two primary intentions behind this feature: first, for the person that has heavily invested time into their alts, it allows them to use those characters they've got an attachment to in their party. Second, it's a compelling reason to make people want to work on alts. You may have noticed that some titles have become more sane, and as a result, more obtainable. Some people choose to interpret this as "dumbing down" the game, and depending on how you wish to look at it, that can be a valid opinion. However, my stance on it is this: I would rather that players have a plethora of achievable goals on any given character, so that finishing titles on one and replaying the game with another character is less of an overwhelming investment.
Having said that, people that purchase Mercenary Heroes are able to set their party lineup as they wish. That is true, regardless of how advantageous that is in actual execution. However, advantages like these are nothing new: it's just the feature that is new, and thus the current song for a dance done many times before. The player that purchases Storage Slots has an advantage: most of the "true" wealth in our economy is held in items (ectos, Zaishen Keys, etc.) and thus being able to hold more means that, technically, you can amass more wealth than another player. Likewise, the person that buys additional campaigns enjoys numerous advantages: new professions, skills, and content. The person that owns only Prophecies is at a distinct technical disadvantage in the competitive game against someone that owns all campaigns. This, however, does not mean the person with all campaigns automatically wins, it only means they have access to more options than the Prophecies player. And yes, these are options that they paid for.
In creating new features that go into the store, we look for things that we, as players of the game, would find compelling. The trick is to find something that is a cool addition to the game, that does not cross into the territory of being "mandatory" or "sinister." Trust me when I say that I have seen many games that go this route with their microtransactions, some even going so far as to reward players with unique items for being the person that spends the most money in the store for that day. The definition of bad is a very subjective one, sometimes gated on exposure.
I've seen terms like "slippery slope" get thrown around. We are not going to suddenly start charging people for items like "+25% damage vs. Humans, OK to use in PvP" weapons. When looking at the types of things I want to see going in the store, I am looking for things that add options to the player's game experience. I feel like things that would have been a selling point feature in a campaign are fair game, because we're following precedent for how the game has already operated. In other words, I would say something like a new profession is fair game - so long as it's not empirically better than any other one that you could be. It's just an option to be something new. By the same token, I would say things like "Increased stat cap" or anything else that makes you explicitly better in an unbalancing fashion is out of the question.
At the end of the day, we are a business. It is our goal to make money. I enjoy getting paid, and being able to prove the worth of the Live Team. I think we have genuinely made this game better than what it was before we started - with fixes, new features, and new content. The overwhelming majority of what we put out has been, and will remain, free updates. Just because we want to make money doesn't mean we need to be jerks about it. Unlike other games, we do not charge a monthly fee + fee for expansions + microtransaction fees. When I see people on the forums posting things like "I'll buy this because I want to support ArenaNet," (and there have been a number of you I've seen) I feel a bit of pride, because it tells me that we've done things right.
That's basically where we're at. We're not trying to break the game, we're just trying to offer something compelling that people might want to have. I know that we'll never please everyone, and some people's opinions won't be swayed regardless, but at least now you know where we stand on things.