I got a couple friends who have had it done. One is recovering from one knee and in October has to have the other done.
I've helped her and the best advice is to do the exercises they give you BEFORE the surgery---no matter how much it hurts. And then do the same after.
And, a little personal advice, after it's all over, I'd do at least 20 minutes a day of weight bearing exercise. At least five out of seven days and a nice leisurely walk will do.