Vehicles vs bushes:
1. bush damage was dropped.
2. "indirect" damage falls off exponentially with distance from impact.
3. Collisions now have a "plow through" behavior where their momentum is more fully applied to the target as necessary, in my testing this meant that you only get stopped by bushes when you're moving at 10mph or less. Ideally even that wouldn't happen with truly massive vehicles, still open to changes in that direction.
4. There's a "reinforced solar panel" item you can make now.
Combat: Martial art styles got a complete rework, and I think all of the fallout from that has been cleaned up. This makes martial art handling more robust, since they're no longer a hacky pseudoitem, and also allows martial arts to be used while armed. I don't think anything else fundamental has changed. This is mostly save compatable, the exception is if you have a style that hasn't been reimplemented in the new system yet, in which case it'll disappear. We will clean this up by 0.9.
You didn't ask, but it'll be relevant to your interests, very recently we had a major rework of vehicle construction that should make things act more rationally.
1. The only thing you can put in an open square is a frame.
2. Components are assigned a "location", which is roughly their position within a vertical slice of the vehicle.
2a. Components with the same location cannot be installed in the same square.
2b. There are some other reasonable rules, such as seatbelts require an anchor point.
3. This is save compatable, existing vehicles in your save should convert over.
One thing that fell out of this (the impetus for the rewrite actually) is that you can now install regular wheels under stuff, and install boards, etc over them.