Flexible - you can you sign up with how much audio time you want to work on. Keep in mind, it's not how much time you want to spend transcribing. It's the length of audio you'll receive.
Pay rates can be pretty good at times.
Feedback from QAs - useful for improvement.
Availability and willingness from QAs to respond to questions or clarifications.
Desventajas
Sometimes the audio files can be very difficult to transcribe due to the quality of file (technical issues, heavy accents, etc.) so you can end up spending a lot more time on a short file.