A little late to the party but I have had a slider for 8 years and have used it about 10 times. About half of those I don't know what I would have done without it. The other half I slid it back (manual) just in case. It seems the longer the 5er the more chance of using it (at least in my case, most of those uses had been since we bought the 35 footer). There are some state parks we go to where all the trees are in the wrong place!
Next time around I'm going to consider an auto slider. I'm a "cover all the bases" kind of guy so take that into account :)