I mentioned I was testing OpenEars in this post, and I also tried Nuance in past few days.
While using both in a quiet room, the response of Nuance seems to be more accurate and the text to speech sound quality is better and more natural. Although it has slight delay as it has to travel back to the server while OpenEars works offline.
Then tried at a noisy train station on 2 separate occassions and the difference is huge! With OpenEars it's almost impossible for it to pick up anything correctly even though I tried to speak as loud as possible - without shouting too loudly as don't want to get too much attention. However, with Nuance, I just need to raise my voice a little and it correctly picked up whatever I said, which is really impressive.
Yes, there are other add-ons available for OpenEars which I haven't tried yet, but even the lowest level of "silver" service level provides lots of things that OpenEars is far, far behind.
There's a small catch with Nuance though, as it's not completely free. For the lowest silver level pricing, it says:
In the production stage, silver service members receive up to 1 million free speech transactions per month per application, after which the cost per transaction is $0.008.
Need to do some calculation - 1 million free speech transactions per month, which is about 33,333 per day. How popular your app has to be to get that kind of volume everyday? After that for $0.008 each, even if your app can get double the amount of transactions and get 2 million transactions per month - about 66,666 per day, with first 33,333 free you will be paying about $267 per day...... Well, I guess if you have an app that's so popular and can generate that much traffic per day, this might not sound a lot, or is it?