RPM TV from South Africa does a video review of the JCW Roadster. [ame=http://www.youtube.com/watch?v=ttuI9KOHih8&hd=1]RPM TV - Episode 197 - Mini Roadster JCW - YouTube[/ame]
Without the spoiler engaged the Coupe and the Roadster are unstable just as the Audi TT was before they added a spoiler to it. There are Retro Fit codes available for fitting the new JCW Fixed Wing that eliminate the spoiler malfunction warnings but I wouldn't drive either above 50 mph without something back there.
Personally I think that yes that spoiler is there for a reason & is needed. At Autobahn speeds I'm sure it is a must have. However if one drove at the posted speed limits it would not be a problem. That being said I for one could not do that.