I had exactly the same feeling when I had my E92 M3 that I used as a daily. I had very few opportunities to use the power and when I was either stuck in traffic or behind several cars in flowing traffic the mpg in the teens/and not being able to use the power just didn't make sense to me.
I now run a Mini Cooper S with a 2 litre turbo petrol engine as a daily, it feels quick enough(although it isn't that quick obviously with only 189bhp) but it returns 40 mpg and I don't get frustrated that I have lots of power that I just can't use, and it is cheap to run.