Just came home yesterday from a one night stay at Pop Century to go to Hollywood Studios and Epcot for the sole reason of finally getting our Magic Bands. I agree with most of rhino4evr's pros and cons but wanted to share my own experiences.
Pros
+Awesome having my room key on my wrist, I'm one of those people that will check for the key 3 times after leaving the room (outside the door, elevator, and leaving the resort) and then every every 20 minutes afterwards.
+Not having to run was AWESOME!
+Being able to do major attractions Toy Story/Soarin without needing to be at the park at opening
+Check ins for fast pass moved without much problem at all
Cons
-Awkward actually using Magic Band, especially to open the door. It seemed like I always had to bend my wrist at a weird angle
-Droid app was not behaving very well, have to re-log in every time to see your schedule, droid app was also placed us in the wrong park multiple times
-Lots of problems scheduling trip before hand
-Major, Minor, Show schedule options are incredibly painful at HS and Epcot. Only one major can be selected at both parks (HS- ToyStory, Tower, RRC Epcot- TT, Soarin, Maelstrom?!?!)
-Phantasmic show wording is misleading, your guaranteed seating reservation means you will be able to sit somewhere
-Failed scans multiple times
-General confusion over what is and is not supposed normal functionality
AP are able to get normal fast passes still. The magic band seems to trigger all associated tickets that are on it and mark them as in the park.