I approve of the way the Guild Wars 2 Living Story achievements incentivize experiencing content. While a few of the mini-game achievements reward aberrant behavior, on the whole the achievements do a good job of directing people towards content, rewarding multiple styles of play, using new content to feature old content rather than making it superfluous, rewarding both exploration and completionism, and not encouraging unhealthy completionism.
As Ravious has noted, GW2 uses achievements where other games use quests. I think this works much better than the early attempt to use the mail system for the same purpose. It also lets them present the full menu of options at once, rather than facing the limitations of the quest system.That has created some heartburn in previous events, when staggered event stages meant that the menu was up before the content was, creating spoilers while frustrating players. The current Living Story content (Bazaar of the Four Winds, Cutthroat Politics) does not seem to have those hiccups. Most games need to put the menu of new content outside the game, and while GW2 also has its updates pages on the web, you do not want to send your players out of the game to see what is in the game. Players can see the menu on the web, in the interface, or by talking to an in-game herald.
The achievements reward multiple styles of play to varying degrees. This is a virtue of both the content and the reward design, and it meets the long-running philosophy of playing as you like. “To varying degrees” probably evokes some grumbles if your interest area has the fewest rewards, but hey, free candy! Achievements for the current Living Story content cover PvP, WvW, harvesting, dungeons, fractal dungeons, mini dungeons, jumping puzzles, open world exploration, dynamic events, mini games, and social content in noncombat areas. Whatever you like doing in Guild Wars 2, they gave you at least one new achievement for it. (Granted, the WvW item is in the WvW jumping puzzle, which might annoy both WvW-lovers and WvW-haters.)
Existing content is integrated into the new content, so the Living Story increases use of the original zones rather than driving players from them. There are far more in the new/temporary area, but you get achievements all over the map. Several are for playing existing content (events, dungeons, fractals, daily achievements) under the influence of the new content. Almost every zone has Zephyr kites, and you use places of power to combine the crafting materials. The big Zephyr kites, each with its own achievement, are scattered across out-of-the-way content, such as at the end of a jumping puzzle or halfway through a mini-dungeon. Granted, I found Forsaken Halls somewhat annoying, but it was a mini-dungeon I had never heard of, and the new achievements encouraged me to go visit it.
GW2 has tiers of achievements, so the same achievements can reward both trying a bit of everything and doing a lot of the one you like. There are also repeatable achievements attached to new mini-games and/or PvP in case you really like one thing. Run the new race once and you get an achievement; run it twenty-five times to get the final tier of the achievement. You get a few free points just for playing normally while the new content is lain over the existing content, a bunch for looking into the Living Story and trying it out, and then there is the meta-achievement for completionists.
I find the meta-achievement healthy in that it does not require 100% completion. Remember, there are achievements for PvP and WvW and PvE and jumping puzzles dungeons and… You reach the meta-achievement before completing all of them. No one should (“should”!) feel “forced” to engage in the parts of the game they do not like, at least not to get the Official Living Story Reward. Let’s encourage everyone to explore the new content fully, but let’s not be ridiculous about it.