Straight up DoD delete? I don't think you'd lose all that much, but depending on how you drive I would think you'd definitely be on the losing side. Any performance cam will net more loss.
Going from stock where I ran an average of 18-19 on my commute, I run 15-16 now. I credit that to the 25 MPH speeds I drive on base (same as before) and low-mid torque I get from the cam, but it definitely is noticeable. Highway went from 28 max to 25 max. May not seem like a huge amount, but it effectively shortens my highway trip length by 30-40 miles.
I loved getting awesome gas mileage in this thing, and doing the cam made me rethink my decision; however, knowing I have fresh top-end parts in my 120,000+ mile engine has been good insurance.