Cybertruck is unpainted (or varnished) stainless, isn't it?

Means that you can't fix small dents with filler, have to swap panels instead.

The cybertruck is unibody, there may not be a panel to swap. Body on frame is easier to fix major accidents as well. But getting a car that retains value andnis cheap to repair means after even major wrecks they won't total it and you get a car back that was bent back to mostly true.

But you can hit the door with a sledge hammer and not have any minor dent to repair. (Just a window)

At what speed does a Toyota Corolla have to hit against your door for it to be the same force as a sledge hammer?

How fast is the sledge hammer moving?

Doesn't unpainted stainless mean you don't really need to fix small dents, no rust issues?

Steel bodywork on modern cars is typically galvanized very thoroughly and/or given other protective coatings prior to painting, so dents generally aren't at risk of rusting. That said, people tend to not like having even cosmetic damage to their cars. It's reasonably easy to hammer out, fill, prep, and paint dents in traditional bodywork, but bare metal doesn't really have that option (especially if, as Elon Musk claims, it's significantly work-hardened--I am somewhat skeptical about that, since it could significantly reduce crashworthiness without a ton of engineering).

Fair, but at the same time we're talking about work trucks a lot in this thread, and I don't think I've ever seen a real "work truck" that was totally unblemished. If it's unblemished you're not working it very hard, in my experience.