With the various 2013 upgraded componentry Bromptons are pretty solid now. The brake levers are now super-long from pivot to end, providing huge mechanical advantage. The rims are overkill. Next I'd like to see a new stem/steerer design that eliminates flex from the stem and allows slight useful flex in the steerer (quite possible). Plus some new tyre options similar to Greenspeed scorchers but a fraction narrower and lighter... perhaps primo comets fit the bill (never used them as they're not widely available in the UK).