They appear to be relatively new. They are off-airport via shuttle bus. Some complaints
here about people being accused of damage and one per being charged a $40 "shuttle fee". It looks like there are at least a few shill commenters that are associated with the company in this thread so you need to keep the post count of the commenters in mind when deciding who/what to believe.
Keep in mind that the damage insurance is provided by rentalcars.com so they are likely to take a significant deposit on your credit card if you decline their insurance. Additionally, they are more likely to "find damage" on return so be sure to take lots of pictures before you leave the lot so you don't end up being accused of causing damage that was pre-existing. If they do hit you with a damage claim, you will have to pay for it on the spot via credit card and then submit a claim to rentalcars.com insurance carrier which can be a pain to deal with.