Double-enter does the high backflip that used to be double-backspace. Looks like they got rid of the regular back and up jumps.
The ninja rope nerf is sad. It's now almost impossible to use the rope to end up higher than the point you fire the rope at. I suppose it could be an intentional decision.
On the upside, the game dir isn't encrypted so there's some hope for modding tools to appear soon. I've already found out how to make custom maps: make a TGA file of 2560x1280 (or vice versa for a vertical map) and put it in \worms reloaded\UserLandscapes. (Sadly you can't use any of them online, not even the ones that came with the game.) And I think it was you who told me people are close to figuring out how to make their own soundbanks.