My rig has the skid wheels, and they are just about destroyed now from dragging going in and out of some of the state parks around here. I guess, all in all, they have prevented the rear end of the coach from taking the brunt of the drag. I do try to approach all grades at a steep angle to avoid dragging whenever possible, but sometimes it just ain't possible.....
As far as gas, I have not had problems when on a trip...both towing a 12' trailer and flying solo. It does take some planning, and I have a new policy of filling the tank upon arrival in the nearest town of our destination in case there is any reason for a mass evacuation. I almost got caught having to evacuate from Myrtle Beach 4 years ago when the big flood happened, and my fuel tank was only about 1/4 full. All the gas stations around were closed, so I was out of luck if an evacuation order was issued.
Tail swing? Haven't really noticed it as a problem. Just watch your mirrors closely and plan for it. Not that big of a deal.