Effective April 1, Brompton is increasing their prices, but not dramatically. The old prices are okay on ala carte orders through the end of March.
My bike personal preferences in order are Moulton, Brompton, then Swift. However, to be fair, I've never seen or ridden a Downtube. Business Week magazine interviewed me a couple of weeks agp on the subject of folding/separable bikes, but I don't know when the article will finally be published. The writer wanted to do a few test rides first.