Before my lift, I would get 22-24 on the highway at 70 mph going from Tulsa to Stillwater, OK. With the 285-75/16's and lift I get about 20 mpg at 65-70mph on the same stretch of road. Around town though, I only get 15 or 16 mpg. Overall, I can't complain with how much it's lifted.
And yes, I do correct for the different tire size when I calculate.
BTW, in my experience, adding roof racks makes the biggest difference. When my 4Runner was all stock, I added a roof rack and my mileage instantly dropped. I thought it might be another issue (spark pugs, MAF etc) until I pulled it off on the side of the highway one day and watched the mileage on my Scangauge go from 16.5 to 22 mpg while doing 70 mph.
I'm pretty sure octane is at work here too. I get right at 19mpg with my '03 Tundra but at least 5mpg less with the '99 4Runner using Regular gas. Tried Midgrade but didn't see much of a diff...