I'm looking at Twillio for a possible future project and this just prompted me to look at Voxeo which I hadn't heard of. The Voxeo website just doesn't work for me like the Twilio one does, it lacks an pricing information (that I could find quickly) and even the developer section is mostly buzzword filled non-information. The Twilio site gives you pricing information up front and the developer pages show you the APIs and give some examples so that you can really see what can be done with it.

This doesn't necessarily mean that Twilio will survive or not have to raise prices but they make me want to use it more than Voxeo even if it has the same capabilities.

I really do hate sites that hide the pricing and documentation or require registration to get them although maybe A-B testing shows that gives better results.