The mechanics have been vastly different, I do admit that. Reloaded is the worst of the bunch IMO. It was hard to maneuver in that game because if you tried jumping onto a bit of terrain that was even somewhat steep, you'd just slide off. The friction was also weird too. Sometimes Worms would barely slide at all, and other times they'd slide like you lubed the terrain with oil. The rope also behaved like the inbred/retarded cousin of the rope from the previous games.
Overall though, I'd say what I've said before: It's not that the mechanics are "bad" per se, it's just that they are different. Compared to W:A they seem bad, but judged on their own, they are what they are. I am in full agreement that the most pleasing mechanics/physics of any of the games is W:A, but W:A isn't perfect by any means. Did you see that thread of weird/wtf shotgun attacks? Most of those simply should not have been able to happen, let's be honest. They are a result of learning the flaws in the mechanics of the game and exploiting them. There's a lot of W:A gameplay that is based around that.
As far as physics goes, the physics model in Rev/CW is far more realistic than that of W:A. Does this mean it's more fun? That's subjective. I like the physics of W:A and in some ways I like the newer physics of Clan Wars. In W:A, the wind has a *much* stronger effect than in the newer games, which I like because it allows for more creative shots, especially with low gravity. Conversely, I kinda prefer the way the grenades bounce/roll in Clan Wars vs. W:A because it's more realistic and just makes more sense. That's not to say I don't like the W:A model; I merely prefer certain aspects of certain Worms games.
From what I've seen of WMD footage, the gravity looks just fine. The thing that looks off is friction/sliding. Also, the animations of the worms while roping look too static. I like it in W:A when you're flying through the air and your worm is tumbling and spinning at different speeds because that really imparts a sense of momentum.
Anyway, I think that WMD has promise. I hope that Team17 knocks it out of the park.