Ride comfort is a very individual thing. When I installed the OME 2" lift and shocks, I was surprised at how much firmer the ride was. It handled much better off road but was not any more comfortable. If your stock shocks are worn out, you may be better off with an inexpensive, after-market shock by Monroe or similar. The OME shocks are a little longer than stock and required an inch spacer under the bumpstops to prevent bottoming of the shocks.
Every modification I have made- lifts, bigger tires, etc has caused a decrease in mileage. When it was stock, it averaged 20 mpg. The 235s caused, maybe a 1 mpg decrease in mileage.
Now with a 3" lift and 30" tires, it's more like 16-18 mpg. When I upgrade to 31"s, it will need to be regeared to a 4.10 to retain and maybe regain a little mileage.YMMV