Make sure you have a good rating with Uber before you depend on them.

"Just as Uber passengers rate their drivers, Uber’s drivers rate their passengers. This fact has been public for a while now—the company published a blog post explaining the policy back in April, titled “Feedback Is a Two-Way Street.” But plenty of customers aren’t aware that they are graded, in part because Uber’s app doesn’t show riders their score (which is on a one-to-five-star scale). To find out, you need to ask a driver or contact customer support."

http://www.slate.com/blogs/moneybox/2014...about_them.html