First things you need to know - there's a big difference between centrally owned schools and franchise schools. I personally believe the majority of negative reviews are from franchise schools, as they do not have as much oversight from central management and can more or less do what they want with the schools. You'll bear the brunt of a lot more bad management, especially if you are from one of the only very few schools in your city. I strongly suggest, if you're applying to work at EF, to avoid franchise.
The working hours can be tough. In non-peak periods you work 5 days a week, with a maximum of 20 real hours teaching. The majority of your classes will be on weekends from around 8:50 until possibly 6:30 depending on your centre. These are long, very tiring days of back-to-back teaching. This also means your days off are on two weekdays. There are benefits to this such as not as many crowds when you want to go into the city and do things on your days off. However if you are a big socialite you'll miss out on a lot of events that only happen on weekends, and you'll mostly only be able to socialise with other EF teachers.
Summer and winter course are gruelling. You will have to work 6 days a week during summer and winter school holiday periods. Your maximum teaching hours are increased to 30 real hours per week. However, if management and communication at your particular school is not good, you may find the sales team go crazy selling more course places than your personnel can handle. You may have no choice but to teach above your contracted hours because at EF, sales always wins, and they are so afraid to disappoint parents and deal with refunds. Also, quite a few schools face a teacher shortage just before summer course starts because some people ditch, leaving the remaining teachers to pick up the slack at the last minute. It's by far the biggest downside of the job and the reason most teachers leave to find other opportunities.
Without the Covid Subsidy, the initial pay is very low compared to other options such as international schools, bilingual schools, kindergartens. Especially when you factor in the amount of hours you need to teach in comparison. It takes a very long time and a lot of dedication for your salary to become competitive.
Holiday entitlement is also pretty low, in fact very low compared to kindergartens or international schools. It increases the longer you decide to stay after the initial contract, but don't expect to be allowed to take it over summer and winter course periods.
Contract termination terms is a topic that frequently comes up in these reviews. I personally believe a lot of teachers simply do not read the contracts that they are signing and end up in situation that are entirely their own fault. That being said however, it is a hassle and has the full intention to make leaving difficult enought to put you off finding a new job in China. You cannot leave without giving a full 2-months notice. That's whether you are breaking contract or completing it. If you break contract, you are also required to pay for your own visa cancellation fees, whereas if you complete your contract you will not. There are two important documents you will need for applying for a new work permit from your new job after leaving - work permit cancellation letter and release letter. EF will not give you the release letter unless you have completed 2 months notice. This is not negotiable so understand this and be aware of the situation before you sign. it's not fair on the teacher but it's what they do. Everything in their contracts they are legally entitled to do - as a big company you can be damn sure that they've had everything lawyered to the max when it comes to their company contracts. Don't think you'll have any hope trying to sue them when you break contract and try to leave in less than 2 months notice and they won't give you your release documents. Plan in advance that you'll need to play their game and can't win otherwise.
A final note - seems a storm is coming for private tuition companies like EF due to new government regulations in China. We don't know right now but a lot will change and may not be for the better.