We rented a boat at OKW last year and took it to SSR, treehouses, and POR. We were able to get there and back in 45 minutes to an hour. We enjoyed the ride a lot! However the waterways are fairly tight and you spend a lot of time slowing down to avoid other pontoons and water mice as well as WDW boat transportation. There wasn't a huge feeling of freedom motoring around.
This summer we rented a pontoon at the CR/BLT marina. We really preferred the experience there. You can cover the entire Bay Lake area as well as 7 Seas Lagoon. We were able to drive by the beach and resort areas for FW and WL and then move over (by taking the boat on the waterway that goes over the road below which was fun!) and hit all the monorail resort areas. We experienced a lot of freedom with large open water areas and cruising at full throttle (which still isn't very fast) without a lot of traffic, which everyone enjoyed. We were gone right at an hour to do this.
Enjoy!