It is a great idea adding Achievements to a game, because it really increase the
audience. Somehow, the persons like more games with awards and are more disposed
to it. That mean persons playing for more time, persons thinking that the game
is fun, and more persons playing the game because this is a great game.

A Menu entry to see the achivements sounds cool, but it probably should be
unique-for-a-character, right? The menu entry still sounds better, because this
don't force Tux to play the game.

The achivements (medals) are persistent and should be sometimes fun, sometimes
cool, sometimes hard to get. By example, us could create a friendly pet and put
it on town. If Tux kills the pet, tux get a medal with the image of the pet sad.

These are things that really should be implemented. Us cannot rely only in
quests, after all.