We really used our park hoppers. Out of seven days, I think the only day we didn't hop was the day we were leaving. We usually did most of a day at one park. We left in the late afternoon for something to eat or just to take a short rest at the hotel. We then headed back for EMH at another park. It really worked great for us. I think it is totally doable not to get the park hopper. For me, that would just mean a lot more planning. I planned part of our vacation around when and where we had meals, but the park hopper would leave a lot more possibilities open. Plus we have a three year old which can require adjusting your schedule. We just like the flexibility. It's also handy if one park is too crowded, you can leave and try another. Also, if it's raining a lot, you can head to Epcot or MGM where there are a bunch of indoor attractions, so the day's not wasted. I think it really depends on your family's needs.
Oh, I should also add that depending on the age of your kids, the park hopper can be a big help. I really expected DD to love MK, which she did, but she was also adament about certain things at Epcot (Soarin) and some shows at MGM. These surprised me and I probably wouldn't have scheduled as much time as we needed at these parks. We spent a long time at Epcot and MGM watching shows, finding characters, etc, and then heading back to MK at night to ride her favorites. I expected her to like AK more, but she really didn't. So, I really wouldn't have been able to plan ahead for her favorites and the park hopper made it possible to do those things!