You should give it a try . I have a 30-day trial account and spun up a couple of services. Well the UI is cool , and there are a lot of templates ( boiler plates ) that you could use to get you app up and running. But you might struggle with respect to documentation depending on what services you use. A lot Watson stuff is in Beta ( you could see it when you login to Bluemix) - and you might have troubles with them.

Beta is certainly beta but if you find problems we will try to fix them as quickly as we can. Real users of technologies tend to find issues with the technology much faster than the actual developers...

The ASR seems to be a bit immature, but the TTS sounds very nice. Any plans to add more voices?

I had to input my credit card once I exceeded the 30-day trial, but I haven't been charged for anything because I'm only using the beta services. And even the Bluemix production services allow free usage up to a certain level, which varies by service.