First GAE was one price. We attended Google I/O session and learned about the virtues of fully using BigTable, so we wrote our application to be tightly integrated into GAE (stupid mistake). Then GAE got a 10X (1000% percent) price increase. Effectively removing the service if you based your business on the initial pricing structure. Now, google is talking about Moore's law and how the service should be cheaper.
Why do I trust google less? Because I don't get a feeling Google has any long-term strategy here. It seems like they're winging it every 6-12 months. In contrast Amazon and AWS have been steadily marching in one direction.
I want to like GCE/GAE, I still run services from it, it's good for some use cases. But in back of my mind, I know google can pull the rug at any moment, depending on the popular flavor of the month.
So what am I saying? Use it at your own risk. It's good for somethings but there are other solutions and there are businesses where cloud services is their main or only business. You know those guys will steadily innovate and build up their services.