I think the only thing the Dahon Vector is killing is the Dahon Mu at the high end.

Personally, I would have been inclined to buy a Brompton instead of a Dahon if it had access to larger winter specific tires - but then it wouldn't be a Brompton anymore, not in spirit with its excellent fold. Basically, Brompton doesn't serve my niche. And for people who love that tiny fold, Dahon doesn't suit theirs.

I like Thor's sentiment. Folding bicycles have enough room to grow and enough breathing space inside the industry that these manufacturers all filling their niche within the niche works quite well.