I became a task rabbit almost three weeks ago. I have bid on at least thirty jobs. I have spent a total of 5 hours checking the site for jobs. I have not been assigned one task. I have applied for several graphic design gigs. Most people want a logo designed for thirty to fifty dollars. Some people want ebooks created from word documents for under a hundred dollars. The hard labor tasks is where the money is. Those jobs depend on bidding low and fast.
It is an interesting place. There are many companies that use TaskRabbit as their recruiting agency. They post jobs that require to sign up on their websites.
Overall, I have to stop wasting my time on it. I intern(unpaid) at a startup that was planning on using TaskRabbit as delivery service. I thought it would be good (could be fun) income.
edit: this is from my experience in Chicago