I'm running 33s and 3.73s LS. I had to trim the front fenders and remove the running boards to get them to not rub. They didn't rub after I removed the running boards but were so dangerously close to the fenders in turns (about 1 inch or less of clearance) than I needed to trim to prevent them catching in a dip or over a bump.
As for sluggishness and gas mileage, I'm not sure what my city mileage is, but I'm guessing it's single digit considering I get about 13 highway. If I drive like a granny (right lane, 5 below the speed limit trying not to break 2,000 RPMs) I can get maybe 15-17 highway. As for the acceleration, I don't think it's that big of a deal at all. If you realize you aren't driving a race car and you aren't trying to smoke ricers at red lights, it's fine.