I really like my canopy which is taller than my cab. I often haul bicycles in the bed and the extra height is really nice. The down side of a canopy is it makes accessing stuff in the front part of the bed a chore. Climbing into the bed to get stuff in the front of the bed just isn't that fun.
If I were to design my perfect canopy it would have a solid flip up door on the driver side with shelves for easy and organized storage. On the passenger side I would have a flip up window for accessing stuff in the front of the bed. I really appreciate being able to look though the rear window in my pickup and out through the passenger side window of the canopy while driving to check for cars when changing lanes (I would not want to give up this view on the passengers side!)... it would just be very nice if the window also flipped up for access to the bed.
I have a 67 Ford beater that I use for hauling compost, bark, dirt, stone etc. If I haul a load off gravel the Ford usually comes home with fewer dents in the bed wall than it went to the pit with. :D I use my crew cab long bed for long trips, towing the trailer and hauling stuff like plywood etc.