We also have the previously mentioned Hoppy Levels. After getting the refrigerator level using a torpedo level, I applied the Hoppy Levels to the outside of the refrigerator. Based on our wheelbase, we can be out of level by 7-8 inches in either direction without exceeding the 6 and 3 degree limits. When we pull into a site, DW goes back to check the levels as we move around to find the most level position. Our personal limits are 3 inches in either direction so we don't feel like we are on a slope when walking around or sleeping.
We carry three sets of the plastic leveling blocks from WalMart, but seldom need to use them. On a 2 month trip to Wyoming this past Spring we needed to use the blocks only once or twice. Our site in Bridge Bay CG in Yellowstone did require most of the three bags of blocks to get level enough for comfort.
Automatic levelers would be nice to have, but considering the few times they would be really needed, I would rather spend the $$ on gas to get to interesting places.