It probably won't do much to reduce driving - and might even increase it a bit - but it's certainly a cost saver for people who can use it (flip the decision between owning and not owning a car for those who don't need one for their commute) and definitely reduce the amount of required parking in areas where it is popular.
Personally, if convenient affordable car sharing didn't exist, I'm not sure if I would own a car now. But with it I have zero desire to have one.
