That's what we do. Have never paid more than $250 for a 10 - 12 day rental (less in off season).
And now, imagine the freedom you will have.
Tired of paying $2.50 or a Snack Credit for a bottle of RO water? You can get a whole case of spring water at Publix for 4 bucks. Grab a 12 pack of beer for $8 - outrageous prices for us Canadians!
If you're on site for 12 days and only have 10 day passes, you can do a day trip - to the beach, the Florida Mall, or eek . . . Universal Studios.
No more 40-60 minute waits for an over-crowded SRO bus back to your resort after the park closes. Heck, most nights, you'll be back in your room, have already had a swim and will be getting ready for another fun packed day just as your fellow hotel mates are getting in.
Don't knock it 'til you've tried it. Rental cars are the only way to go.
Now I just have to take that next step in the evolutionary process and get out of the on-site rut and start staying in a bigger, better, slightly off-site room, like Bonnet Creek. Maybe this year. I know that once I do, I will never again stay at POP. Or any other over-priced Disney room.