Mark me down as a definate hopper. Though the larger the group I'm with, the less we hop.
When it's just me or one other person, it's a brezze to get from park to park. Never takes more than 20 minutes. I just hate large crowds, and I also have definate moods - some days I want to ride tons of rides, some days I just want to see tons of shows.
For instance, I've found the best combo to be going to say MGM in the AM, hopping over to AK late afternoon (say 3PM), leaving AK at 5, going back to the resort for a rest, then going to Epcot or MK if it's open late. That's three parks in one day, but done correctly I can ride tons more rides that way, or see every major show between the parks.
That helps me hit a park during the less busy morning hours, take advantage of the non-existant lines in the rides at AK after the afternoon parade, and see another park after dark.
It's not an every-single-day thing, but done effectively it can be great. First time visitors, however, I'd say don't hop more than once per day - say one park during the day, another at night. But once you've been there enough, and have a good idea of the layout and have experienced all the parks before, you can really hit a whole world full of favorites in one day if you have the stamina.
I have to admit, since I've been a passholder I've never not park hopped on a day I've been down, except in the rare instance on arrival or departure day when I only have time for a short hour or two trip to a final park.
N.E.D.