If you haven't noticed by now, I am an advocate of talking to your computer. I regularly use the dictation software and have been more and more using the voice search capabilities. I am also using headset and microphone for participating in GoToMeetings and Skype.
If you are going to be talking to your computer regularly, invest in a decent microphone. I initially tried to use a cheap microphone, and had poor results. It was discouraging and led me to initially shy away from this use. However, due to my specific need to be able to talk to my computer for conference calls, I knew I had to make it work.
Investing in a decent microphone made all the difference. Dictation recognition skyrocketed, calls were much clearer, and voice search better understood what I was saying. I'm not saying you need to drop $100.00 on a microphone/headset, but don't buy a $5.00 microphone and expect great results.