This is widely used on most forums to give members awards and things, (including the EoTM and awards for W/FoTM here) and continues to be something that more and more forums are adding. What kind of achievements do you have on your forum?
I've had an awards system on my forum but something about just wasn't working. It might have been the general awards I had on it rather than awards that were particular to the forum, however I did have post awards that were automated (thankfully) and that seemed to be something members liked.
I think it's important to make awards that aren't related to post count. An example of this would be a Patriot award (maybe the image for it could be an American flag). It would be received for logging in and making a post on the 4th of July. Similarly there could be a Halloween award with a Jackolantern image. I like those types of awards.
I also think that awards can be highly unique. They shouldn't all be automated. If a user goes above and beyond in their efforts to help you improve your forum, give them an award or achievement that is shown on their profile/posts.
Achievements should not just be about how many posts you've made and in order to keep them important, not all of them should be obtainable forever. Some achievements should have a limited time availability so that newer members work harder to gain new achievements, knowing that they might not be obtainable in a few months time. Not every award or achievement should have a time restriction and you shouldn't tell your members when an award is going to become unobtainable. Let it be mysterious, it will make users want to get those achieves even more!
