I really have nothing to add but will comment anyway.
We use Zipcar almost exclusively for transportation. When we take long trips, we compare Zipcar to Avis. (Avis has a branch at Back Bay / South End subway station, about five blocks from our apartment.)
At Christmas, the cost for a three day rental using Zipcar was ~$280, which included gas and insurance. Avis was about the same. Usually, Avis would be less but demand must have been higher or something. Zipcar has higher rates on weekends versus weekdays, I believe, but the rates are consistent otherwise, which is nice when planning a trip. I assume Avis changes its prices weekly if not daily?
When gas prices skyrocketed the past couple of years, I feared Zipcar would have to raise its prices but they've stayed around $10-$13 per hour since then.
Their profit margins must be low (which I think the articles above mention) which would annoy investors, but there's really no way to economize - the cars (by design) are all over the place, requiring a fleet of workers to clean and maintain the vehicles. Including gas is, of course, also a major factor in whether or not they make money. They include 180 miles per day and the vast majority of users probably go a fraction of that. We went 480 back and forth to NY State in three days so were below that, but I've gone above it before.
Each person found a different reason to use Zipcar; for me it was all about convenience - there were eight or so cars within half a mile of home, another 20 or so spread around downtown.
I would pay a bit more to continue to use it if they keep them located where they are (or, hope against hope, add more locations). I can only assume they're going to reduce locations (get rid of the bad spots) and raise rates. Anything less than $20 per hour would probably work for me, but I'm sure others would freak out.
