@mini-williams: Specified the brace at original order stage; cost was £165 I think?... I was not charged for fitting (being brand new/fitted pre-delivery by Dealer, guess they absorbed this cost?)... But I think the labour time is only half an hour max though.
@DerekH: I've got Sports Suspension, and per above comment the brace was fitted before I picked up car (so can't compare before). Also, it's too early to say (only got 200 miles on clock since picking up last Saturday). But, personally coming from recent previous cars such as BMW E46 M3 which have these kind of things as standard - ie braces, diffs, stiff suspension, etc. - then have to say already I'm well impressed with my Cooper S. There's a photo of my car in
http://www.mini2.com/forum/2959845-post93.html