There has been talk about achievements in Elemental before (can't find the thread though...). I think the consensus was that as long as they don't give an in-game bonus (Like plus to attack, defense, ...) most people wouldn't mind if they were included in the game. The problem which some people had with achievements giving in-game bonusses, was that then to be competitive, you are more or less forced to complete them.

So, I'd like for some achievements to be included with some cosmetical rewards that show other users (in multi-player) what you achieved. Some new options for the Coat of Arms, Weapons / Armor that looks different, but is the same as the standard version in stats, special mounts, ... Things like that...

I for one would like to see some acchievents reveal art and areas of the game's lore... like if you kill X number of BlackWidows you get access to some interesting (but devoid of tactical value) text that explains what BlackWidows are and why they act/look the way they do....

I see your concerns and I agree with them too, but, I don't think Stardock's that stupid. I haven't seen a game of theirs that didn't have great depth and lore to it. Even without the lore of any given game Stardock is great about giving us features. If anything an achievement would just be another "hey, that's cool" feature without distracting from any other game content. That's why it wouldn't be a good idea Imo to add bonuses to achievements. As Scorpiana already said, then everyone would have to get them to compete and that's not fair to some players.

I'm just envisioning something that's just fluff on top of the actual game.  We're going to be spending an inordinate amount of time in beta (supposedly hooooooribly painful time per Frogboy... sorry, I do try to stop having fun, but it's a challenge) so the actual game is going to be solid regardless of the achievements, but as long as they're non-gameplay changing, then they could be very fun and wouldn't detract from the core game at all.  I know I got a chuckle out of the "He no nuts, he crazy" achievement in Lego Indy for breaking X number of objects, so similar just for fun things would be nice.  Completely pointless, but fun, should be the rule.

As long as the rewards are something along the lines of avatars for the forums or skins or such for in-game, or just badges ala GalCiv2, then they're just a little fun extra.  And as others have pointed out, if they're something we can mod, then so much the better and that'd be an excellent avenue for creativity.  Just need to have a non-gameplay-affecting skeleton in there to work with.