We always use the park hopper at some point while we're there. That said the ticket we're buying this time are for unlimited entry during the 14 days we are there, park hopping included.

We don't hop every day, for example our first day is normally Magic Kingdom the whole day. However there are things we like to do such as parking at MK, taking the monorail to Epcot and then finishing off at MK for the parade. We do normally spend two days at AK but normally they are part days where we switch to somewhere else when it gets too hot. Another one is for Fantasmic, we see it each trip but not necessarily on the same day we were at MGM, so it pays to be able to arrive after a day at another park. Sometimes with the MGM and AK plans they hare a day with one of the water parks, not sure if doing that actually requires a park hopper though.

Basically we like the flexibility it offers.