I thought there are some additional Fastbreak benefits:
1. The ability to enroll in Budget Bucks
2. The ability to add your Frequent Flyer or other loyalty program to a card online (if you do not have Fastbreak you have to present the card at the counter)...
Not sure if "Rent More, Save More" is tied to Fastbreak too. I think it is. Once in a while it is cheaper than other codes I try.