Maybe in the future, some 'live' achievements would be good (if possible). Just like in Steam/Xbox games I believe. If you do something, you get popup window in the corner. Like I don't know - kill X enemies without taking damage and boom, medal appears in shiny glittering window. There could be some ideas for that, but I know it's more like a joke. Copying pattern from modern games, which doesn't rely on skill that much, wouldn't fit Roguelike idea at all. And it's annoying for some gamers (compare to WoW achievements, some hate it, but they encourage to explore things you wouldn't normally). Anyway, you will find out upon ending of the game, if you got some medals.
I personally like idea of collecting stuff - it kind of gives another meaning to your normal games / YASD. But hey, we have ranks for that, don't we?
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On the other hand, some in-game indicator would be nice, like - how much damage we have taken. Maybe not how many enemies are alive, but how many we've killed.
Achievement: Gib 500 corpses - EXTRA CRISPY!
Eh, remembers me of QuakeLive achievements ;)