I'm a radiologist who uses a Nuance product for several hours a day, every day, and my experience has been overwhelmingly positive. Whereas I used to waste a great deal of time editing and correcting mistakes by human transcriptionists, I only occasionally have to manually correct the Nuance transcriptions. Our throughput and efficiency have increased considerably since we started with the product, and there is absolutely no way that I'd ever return to the previous system. The adoption of speech recognition has been the biggest advance in my field since digital imaging, IMO.
Oh, and "when the software is confused it tries to select something that is grammatically plausible"? I don't think so - the software has no concept of grammar.