Gandalf Parker advocated the notion that learning to play the game well included learning how to adapt to changes on the fly. He used to run randomized games where certain unit stats were given random values (maybe archers have Prot 18) and you don't discover this until you encounter some. I don't do this myself but that's partly because I'm still learning the basic game.
Some people like games which force you to make decisions under risk (i.e. you don't know whether you'll succeed but you know the probabilities), others like games where you make decisions under uncertainty (where you don't even know the probabilities). I find the latter category fun but nerve-wracking. It's like the first time you try out a new magic item or spell--will it be worthwhile and win you the battle or will it just get you killed? I've been surprised in both directions.
Note that intel-gathering on capabilities becomes much more important in Gandalf's chaos-style games. In that respect it resembles real life.
-Max