It'd be interesting to see what kind of mad-dash there'll be on XBL when this comes out with people trying to snag the #1 leaderboard achievements before other's get a chance to play.
I'm still up in the air about achievements like that.
-On on the one hand you can't view leaderboards outside the game so having that as an achievement will let you show that off anywhere (though this is more of a solution to an MS problem of not being able to view leaderboards outside of a game)
-On the other hand it's leaves the obsessive compulsive like myself feeling somewhat hollow knowing that you'll never be able to earn that achievement, and never be able to 100% the game.
I think I've decided that I don't like Xbox Live based achievements in general. It excludes those who don't have Xbox Live Gold. IMO Leaderboards are good for showing off on Xbox Live, Achievements are good for showing off outside of Xbox Live.
I look at it this way, I have friends who can't have Live Gold because they don't have fast enough access available, they're able to do silver (and spend hours downloading a small Arcade game or patch) but not Gold. Also Gold can be expensive for some. How would you feel if there was an achievement that you could only earn if you had a hard drive, or if you had an HDTV.. and you didn't/couldn't have those thing.
I'm all for hard(er) achievements too, but not ALL of them. I think COD2 is a good example. It gives you some for playing through the game on a normal difficultly, but it also as a whole lot for those who play through on a the really touch level and prove that they've truly mastered the game. It's difficult but not impossible to 100% the game, and you don't have to have Xbox Live Gold or anything more then a core console to do it.