Last week I read somewhere that you can't tell the difference between the 50i and 35d in 0-30. Actually, you can, but the Ds show really well up to 0-50 mph.
Quite a shame that we will see a hybrid before we will ever see a 40d or 50d in the US market.
Note: where data was unavailable (such as regulated max speed on US cars), I used data from the European equivalent.