I've had free rentals for recall and campaign repairs, but not for warranty repairs under the original warranty. but, got a 12 day rental [1500 hemi] covered during recent warranty work under the extended warranty. don't know how many days were covered by the warranty and how many by the dealership, but the bill was written up as if all 12 days were warranty [came to just under 10k all in - heater coil, supercharger, and a few other parts that failed/broke or were found to be bad during repairs]
Edit: may depend on the dealership and/or the mood of the service manager