Mileage reimbursement is nice if you run a cheap vehicle.
I worked for a while at a small IT company, and rode a late 70s motorcycle everywhere. Cost me around $0.05/mi in fuel, and since I did all the work on it myself, it was fairly cheap to run in terms of money as well (pretty expensive in terms of my hours, but... it wasn't like I had anything else to do with my evenings, and it beat sitting inside in the cold - this was during the "I can't justify heating the house except to keep pipes from freezing" part of my life, which I'd add my ferrets *loved*).
For what it's worth, a lot of our customers thought it was cool as hell that their IT guy showed up on a motorcycle in a leather jacket. :)
One particular paycheck, I'd had to make a few ~100 mile round trip runs to a remote office. As the guy doing the paychecks was looking over that, he asked, "You took your motorcycle for all these trips, didn't you?" Me: "Yup." Him: "You're really making out on this mileage reimbursement, aren't you?" Me: "Yup." I ate well that week! :D