For us, a locker at each park is critical.
We park-hop, so we are at each park at least twice (or more) per visit. So, I generally take our cameras with me for part of the trip and take all of the pictures and video. Then at other times, I put the cameras in the locker and just enjoy myself.
I carry a Nikon SLR and a Sony miniDV video camera, so it certainly gets bulky. We also have a "point and shoot" camera that we can slip into a pocket for emergency photos, but I use my SLR for all of the important ones.
I get pictures and video of all of our favorite rides, places, and moments during the designated "camera times." Then when we visit the parks a 2nd time, I leave the camera in a locker and just enjoy myself.
The great thing about park-hopping and lockers is that you only pay once per day. Thus, if I rent a locker at Epcot in the morning, then I can easily transfer that to the MK for the evening without paying extra.