The Ti conversion was really a vanity project for me but the steel rear triangle is a pretty unsightly part, especially when scuffed and rusty. The Ti parts are a lot better finished; the fork crown was perfectly cut and the welds were neat.
The Ti seatpost, at the price I paid for it on a new bike, was rather more worthwhile for weight saving, especially in the three-inch longer "extended" size which I need (pulled right up to the stop gives the perfect 30.5" saddle top-BB spindle height for me; the standard length post is too short for most men). I don't think Brompton's flirtation with alu seatposts went very well at all as it was so short-lived.
Brompton could make things a lot easier by bolting the chain tensioner to the frame so it's no longer concentric with the axle (like a derailleur bike) but the need for a toggle chain and anti-rotation fittings (needed to counteract the torque differential in the hub from any gear except direct drive) is always going to militate against very quick removal*. Actually, you could redesign an awful lot on a Brompton but when they can sell the basic ones for nearly a grand each as fast as they can make them, there's not muh incentive. And I suppose backwards compatibility is a plus point; imagine having to carry "old" and "new" components for everything, currently only an issue with things like LWB and SWB cable outers.
*do the 1- and 2-speed bikes have anti-rotation washers? They're not necessary to stop rotation in use but I suppose they make it easier to tighten the axle nuts.
