I love Fast Pass. We use it for 2-3 attractions a day. Not huge, but it greatly increases our enjoyment of the parks because we use the time before our visit window to do other things besides wait in line. Park Hopping, in my mind, becomes easier because if you arrive during the afternoon at the MK, you can still ride Space Mountain without it taking up 90 minutes of your day. And if that's the only attraction that you grab a Fast Pass for, then you can "plan the biggie", and really enjoy the smaller attractions that you would have missed. It adds tremendous flexibility to our visits.
I do think the stand-by lines are way longer in general. I just never wait in them. I plan my day around the 2-3 attractions that have Fast Pass, and then do the remainder of the park at my leisure.
The only real down side? If you don't understand the system (And DisneyWorld gets many infrequent visitors), and you visit on a busy day, you can really get jammed by Fast Pass. And if a popular attraction's Fast Passes are all gone, then you can REALLY be looking a long wait for a super popular attraction. (Look at Soarin'.)
But I understand it, and it makes my visits much more enjoyable. Pirates doesn't need it.
