I agree with ThinkTink. We go for 10-11 days each year and get 7-8 day passes W/O park hopper. We used to get the hoppers but found that we end up spending too much time traveling between the parks. We are not WDW "commandos" as are other that try to hit 2-3 parks in a day.
I would hardly call my family "commandos" for going to two parks in a day :lol: I swear sometimes we're the most relaxed family at all of wdw...just take it slow, we'll eventually see everything, eat at some point, go where we feel as we feel and that means park hoppers are a must have for us.
Having the park hopper actually gives you a bit a of mini-break in the day rather than the families who try to cram every single attraction in one park in a day. The trip on the monorail from MK to Epcot is relaxing, a chance to chill out a bit and decide what we would like to do next.
The boat ride from Epcot to DHS is a nice relaxing ride as well and we get to save up some energy that other families waste running around the parks at full tilt. Besides, at the end of one parks day, if you still have energy and wish to go to a later park you can instead of being disappointed knowing the Epcot is open late but you can't go.
Traveling from park to park is relatively easy, not the hassle that some people make it out to be and before you say "But I have kids!!!!!" My last trip was with a group of 11 people with kids aged 11 months, 3 years, 5 years, 9 years, 10 years and 12 years and we park hopped 5 out of 8 days there.
It's definately worth the money to avoid the disappointment of not being able to do what you want to do in a day because of the limitations of one park. Unless you're on a super strict budget and simply can't afford it (which is understandable) I would get the park hopper.
It also helps when you're on your last day and there's two or more attrcations that you just HAVE to do again before you go. that way you don't have to say "Well, I wish I could do Soarin' AND PotC one more time but I guess I'll have to choose"