It was suggested to me by a co-worker that if there was a work emergency, the cash saved ($17 shuttle ride including $2 tip) by the company would not have been worth the 100 minutes of not being available.
Even though my company can well afford and approves of higher priced transportation including weeklong rentals, I have never been one to take advantage when a deeply discounted option exists.
We disagree on the value of time, apparently.
I'd say renting a car is the compromise here. You are in control of you time at that point, and you have the flexibility of transportation anywhere, anytime.