I used Dragon Systems for quite a while and with very careful attention to my speech patterns, I could reach an accuracy rate of about 80%. Then I stumbled upon an on-line dictation service that uses real live transcriptionists and charges a fraction of what the software cost me.
The service is iDictate and is located at www.idictate.com.
It is nearly error free and I don't need to learn any strange commands. When I want them to "go back and underline the last sentence", they do.
My standard method of input is over the phone, but you can upload a variety of files via email.
For most jobs, they charge one-penny a word (US). You can upload templates, letterhead, special forms.
In short - I love the system and it works SO much better tan any voice software I've tried.