I've worked for a few ESL companies, and QKids is the best!
I've been working with Qkids for 2 years. Qkids has changed a lot in the past year. They listen to there teachers, and are constantly updating the software to make lessons go as smooth as possible, and they are very understanding about tech issues. If you are unable to teach due to tech issues, they remove the absence (no fees or penalties) and try to help you fix the problem.
Also, Qkids assigns all your classes! So if you say you are available to teach 4 classes a day, they will give you 4 classes a day! No 'trying to get bookings' nonsense.
They may not be the highest paying company out there, but there lessons are the best by far! Very interactive with songs and games you can play with the kids!