I like Ctrip and book all my travel through them. I've had great service on the phone from them when things go wrong and I actually like the mobile app for booking flights and hotels. I've never had a problem with them, knock on wood. I book both domestic and international flights as well as hotels on the mainland, in HK and Macau through C trip.

They also have a points program that doesn't offer much value but offers something, I got a free night at the Shangri La Shenzhen wiht all my points.