It is a great way to make extra income, just not something to rely on to pay all of the bills. There are many tests available to try for, but this does not mean you qualify for all of them.
Its a great gig if you're going to be on your computer all day anyway, seeing as you'll hear a 'ding' when a new test is available to try for. I like to use it while searching for other jobs.
You are paid fairly, about $10 per twenty minute review, it's just you may only get one an hour or every hour and a half. You can always come back to it if you have been gone from it for awhile, just review the tutorial and you'll be on your way, meaning the job security is spot on, but I don't see how you would advance in the company.
Overall a great site to check out if you need to supplement your income or have extra time after work, but not the job you need to support your life (most likely).
Also, I find recording the reviews to be a lot of fun and the time goes by very quickly. I'm thankful for UserTesting.
Make your own schedule, Fair payment
Not reliable, No benefits