It's a really cool idea, that works really well. I wish it was more nervous though, so here are some suggestions if you want to go in that direction:
- make the player move faster
- make the bullets bigger
- automatically roll the best die available when a weapon's ammo is depleted (or make a system where the player can select what die will be rolled next): pausing the game that often cuts the action too much in my opinion
I would recommend this talk from one of Nuclear Throne's developer on how to make your game feel better to play.