I have tried Grimm a few times and like it very much. However I never played it like it is in the books. E.g I never used advantages and disadvantage, class abilites and weapon rules. They were just to many small extra rules, which complicated character generation and slowed the game play down.
Instead I once used something like plot points. I gave the players 5 points that they could use to get a bonus on a skill roll. It worked great.
A second or revised edition of Grimm would be awesome, that is even less influenced by D20.
What have you done with the game?