Though butterfly/scissor/gull wing doors may be cool (certainly attracts attention), our cars were never designed with them in mind. OEM designed like Lamborghini or Mclaren are probably much better designed than retrofitting special hinges onto an existing car. Also, I've heard that generally the ingress and egress is more difficult with these doors. Lastly, some people think it is an advantage that with these doors, you can fit into tighter parking spots... but that just means whoever you park next to will usually leave you with a nice door ding.
Jason - can you provide me (here or in a PM) on your impression of the I8? That car has intrigued me. In the future, I plan on getting a ALFA Romeo 4C, but have considered the I8. I am a hardcore sportscar fan, but also have a green/eco side and thought maybe the I8 would cover both interest. Or, it might just muddy both sides and try and do too much with one tool.