Pros
Tutor.com is a fairly good way to make a little extra income on the side, tutoring subjects that you enjoy. Pay is on the low side, but a good amount of time is spent waiting around (especially if you're a floating tutor, more on that later) so if you're good at multitasking it's not too bad. So far, I haven't had an experience with a bad student, although I'm not sure if I'm just really lucky. The entrance tests (you need to take 2, at least one in a subject they mark as "higher demand") are fairly easy to pass, and after a mock session they set you up as a probationary tutor, limited to scheduling 5 hours a week. It's not too hard to get hired and start working for them as a probationary tutor. Mentors are quite helpful, if a little nitpicky sometimes. I've heard some stories about bad ones, so it seems like a bit of a toss-up for who you get assigned.
Cons
Here's my single biggest gripe about Tutor.com: every week, the different tutors have different scheduling times. Tutors level 2 and 3 schedule their hours at noon on Wednesday, tutors level 1 schedule at noon on Thursday, and probationary tutors schedule theirs last at noon on Friday. This means it's basically impossible for probationary tutors to find hours. For about 3 weeks, I've tried scheduling my hours exactly when it opens up to probationary tutors, only to find the schedule's completely full with no available hours. Tutor.com doesn't open up enough slots for all tutors, meaning many tutors have to try "floating", working unscheduled hours. In theory, this gives tutors a lot of flexibility. In practice, it doesn't work since student demand for tutors rarely exceeds what the scheduled tutors can handle. Therefore, very little "spills over" to floating tutors. The student user base is not exactly small, and given what Tutor.com charges the students (about $40 an hour) they are certainly more than capable of opening up more time slots to tutors, especially in high-demand hours.