Exploitative system, extremely hard to get work at first as the site is oversaturated with tutors, technical issues.
You are totally at the mercy of parents'/pupils' reviews, especially when you start out. Although there is a 5* rating system, you will usually be rated 5 or 1 star. Most regular tutors on the site are rated 4.5+, so you can only afford 1/20 bad reviews before you're knocked out of the rankings. I've never received a negative review, but I've dealt with difficult and aggressive parents who demand an unfair amount of work from me (and I've seen other tutors report similar severe bullying). This means you need to accept whatever poor treatment you get until you have at least 15 5* reviews, or you're going to struggle to get any teaching.
The site takes a huge cut of your pay and doesn't make this clear to parents. I've had multiple parents complain about the high prices, not knowing that only a max. 2/3 of that is going to the tutors.
Building up enough reviews to get work without refreshing your email every 30 seconds (I'm not exaggerating -- you literally only have that long to respond to some of these ads) is extremely hard. Unlike a lot of tutors on the site (who are mostly undergraduates), I'm a PhD student with teaching experience. This puts me at a major advantage for getting work -- however, it still took a month of constantly refreshing my email for offers and accepting any pupils I could (which often necessitated teaching on texts I didn't know and therefore had to read & prepare in advance -- that translates to hours of prep for a lesson) in order to make any kind of money from the site. If you're an undergrad with no teaching experience it's going to be very, very hard to get started.