I just did a one-way rental with Hertz from DCA to BWI, and I have to say I liked the new BWI facility, but then I was returning, not departing.

And I was returning at 5am on a Monday, so traffic was light from downtown (Hyatt) and the Gold Counter was empty of customers, so quick processing on the return and the shuttle bus to the terminal was ready and waiting for me.
I agree DCA is really nice, as well. First time I rented from there and easy access to the interstates.