Yea, when I play NFS games I take the realism with a large grain of salt. For instance in most wanted, a fat Lambo had a tighter turning radius and better handling than an equally specced elise...
The lotus can really get 40MPG? granted its your mpg, for me it would be like 33 which is what I expected it would get if you didn't push it.. EPA says like 23 or something combined city and highway, but they include running AC and probably running 4 second acceleration times instead of a more realistic time, so 33 is probably possible (sounds like second cam is at 4.5krpm.
Practicality is like none with its trunk that is like as big as a sheet of paper ;)
One thing I like about the cayman over the carerra is that it has the standard porsche front trunk, but also a back trunk because the engine is infront of the back wheels and basically right behind the front seats.
http://i.pbase.com/v3/57/440357/2/49478421.TrunkfromOutside.jpg
I've always thought the US economy ratings were a bit strange, I'm really not sure how they're measured. It must be a lot more than just the octane rating. I know over here the mpg ratings are best case scenario, and you'd have to work very hard to get those kind of ratings, I guess they stress the cars a bit more for a more realistic rating.
That said, if I'm trying to save petrol, I drive in an entirely different way!
I was talking to a guy with an Exige Cup at the Nurburgring and I said I managed to get 38mpg on my way down (which I was very impressed with!), and he said he'd managed over 45! You're talking motorway driving there though, lots of constant cruising (it's still only a 1.8 engine in a light car so it wouldn't surprise me too much).
I agree about the Cayman, the mid-engined layout helps the handling a lot, much better than that unwieldy rear engined 911. Lots of tuners claim the Cayman can be far quicker than the 911, but Porsche refuse to acknowledge it, and in many racer, refuse to give drivers any support when they choose to use a Cayman instead of a 911. I'd still love a GT3 RS though :).