"while maintaining great gas mileage. "
I think this is relative to your expectation. While I am very happy with the driving dynamics of my xDrive 28i, but like many other owners, I've never got the City/Highway 22/33 mpg stated. The best I got is about 20mpg with mix city/hwy (60%/40%) driving. Some others got higher numbers but not many get close to promised.
In terms of space, I was able to load a 46gal fish tank with stand with rear seats down. Can't complaint.