Honestly, I have not lost fuel mileage with it gone. I have tracked all my fill-ups with aCar since I bought the TB. I am averaging (long term) 13.6 mpg. It's winter now, so winter gas and idling has me around 10.5-12 these days. Last complete fill-up to measure was 10.6 mpg. DIC is at about 11.5 at the moment, and it is usually within a tenth or 2.
The added benefit is never having it kick in and start the process of the engine burning oil, which would be worth it to me to lose a few tenths in mpg over the life of the engine/truck. Since I had mine turned off, I am using less oil. I'm hoping my engine can recover and get into a "normal" consumption volume. My first oil change saw me adding 6 qts of oil between changes (5300 miles). The last oil change interval (4500 miles), I only added 3 qts. Your engine may not have suffered this malady, but it seems like a large percentage do. Sounds like something like that might have happened to you if your engine seized.