The ease of use for creating voice applications using Microsoft Speech API with support from AWS Lambda functions.The ability to create custom voices very easily.Very good documentation provided by Amazon. Nothing as such but if you are looking at developing any kind of Voice Application then definitely go ahead with it. I'm working in building call centers where we need to provide customer service through IVR or voice channels. It's been great experience so far because its easy to integrate and has lots of features that can be used across all kinds of projects without much hassle.