Minor, not major changes result in the best improvements in speech recognition performance. With continuous speech recognition, the dictation of complete thoughts improves the recognition. For a time, IBM VoiceType boasted that it considered three words at a time in order to choose the correct word. DragonDictate at that time only considered two words. Dragon NaturallySpeaking, sometimes very visibly, considers all the words in its buffer before it decides what it will commit to the document.
Speech recognition is certainly a moving target.
What was true about speech recognition two years ago, in some ways, hardly applies. The price has dropped dramatically. Training is still advisable for top performance. In practice, the majority of cost is in hardware, training, and then software. Seven years ago you could get a computer and speech recognition software for 15 thousand dollars.