I'll give you as much information as I can.

Wall Street English has three types of contracts. 1, .7 and .4 1 works 35 hrs, .7 works 25 and .4 works 15.
I'll give a typical schedule of a 35hr contract. Each teacher is basically on a two week rotation. The first week is 5 days (two days off) and the second is 6 days (one day off plus two half days) so each week has the same working hours.
You HAVE TO work weekends. No foreign trainer can take a day off at the weekend unless it's annual leave or a holiday. Remember, most of the clients are professionals and they have their own jobs to do. This makes weekends and evening the busiest times. I know of plenty of teachers with families and some of them hate working weekends and end up quitting while others seem quite happy with their situation. Split shifts are also rotated. I currently have one split shift every two weeks (10:30 - 2; 6 - 9:30) I don't mid doing this as I live near my centre.

Salary is good and always paid on time. I've never heard of anyone getting paid late. The only financial issue I've heard was one teacher did a lot of overtime and the company forgot to pay him one month and then paid him two months of overtime the month after, unfortunately this bumped him up into the next tax bracket and he had to pay more tax. The company rectified this with a one-off goodwill bonus.
Airfare is not paid. However a yearly bonus for contract completion is paid. Currently about 8,000 CNY which isn't a lot I admit but most teachers don't go back to their home nations.

I've not heard anything about teachers not having enough classes to teach and not getting paid accordingly. This must be hearsay.
Wall Street English is expanding rapidly and will always have clients. The target is to open another 50 centres in China by 2013 bringing the total up to 99 centres.

I hope this information is helpful to you.

I've worked as an English teacher for 7 years now, in the UK, Korea and China and Wall Street China has a solid reputation as a business. The only horror stories I've read are about Wall Street in France. Another fact about Wall Street China; it breaks and sets international benchmarks for sales and satisfaction!

Bob