I'm not an achievement whore by nature. In fact, generally I find the very existence of achievements abhorrent. Most of them, in my experience, are just there to reward repetition of mindless tasks or to give me a meaningless pat on the head for doing things I was going to do anyway, like complete a level or build a unit. And I have no patience for most games that force me to do some task X number of times to unlock new content - and yes, that includes Team Fortress 2.
But with StarCraft II, I'm out to get them, but not just to have them. I'm using them for a different purpose: to make the game harder.
I decided from the start that, after waiting 12 years for this game, I was going to drag out the experience of playing the campaign as much as possible. To that end, I'm playing through on hard difficulty (I usually play on normal, 'cause it's the normal thing to do) and challenging myself to not just beat the game, but to beat the living hell out of it. I aim to hurdle over the raised bar of earning all of the achievements.
I'm roughly half way through at this point, and I've found that, aside from the usual “complete all the mission objectives” achievements, StarCraft II does an excellent job of avoiding lame grinding achievements. No “You've built 1000 Marines!” or “You've harvested 1,000,000 crystal!” Those would be pointless—play long enough and you'd earn those with no additional effort. Instead, they give you two extra goals you must accomplish per mission, like winning within a certain time limit on hard difficulty, getting through with your stealth hero untouched or killing an enemy you might've otherwise avoided. They're tests of skill (and/or persistence), not tests of patience. It definitely makes things more challenging—insanely challenging in some cases—and it's definitely extending and enhancing my StarCraft II experience.
There have been a few that have thus far escaped my grasp, though. For example, the Red Lobster achievement on the Devil's Playground mission, where the objective is to kill the mega-Zerg Brutalisk by luring him into the low ground just before the lava rises. I'd actually achieved this one a couple of months ago during a visit to Blizzard, but somewhere along the line someone tweaked the Brute's behavior. Now he seems so nervous about the 30-second warning going off that he wouldn't chase my Reapers far enough to get caught in the lava. The most I could do was singe his toes a little, but he still managed to escape before even reaching extra-rare status. This drove me nuts, since I was only able to attempt it every four minutes, making every failure extremely time consuming. (Yeah, I could save and reload over and over again, but that's just not sporting.) Eventually I gave up and moved on, so I'll have to come back and try again later to get my satisfaction.
I'm currently on the last Protoss mission, which is going to be a real bear to accomplish. If you've played it, you'll know why.
Other than a smug sense of self-satisfaction, have achievements ever improved your gaming experience?