Is it possible to clone the operating system to a different machine? I have spent a lot of time setting up a speech recognition profile which would be a pain to do all over again. I have configured this on a Mac mini. Suppose I now wish to buy a MacBook Air. Would it be possible to transfer my entire current setup including software and settings across to a different hardware platform?
Yes, it is possible to clone the OS between machines. SuperDuper! or Carbon Copy Cloner are the recommended ways to do so. Make sure both machines are on the same OS version (i.e. 10.7.3) before you do so.

However: Migration Assistant is really good. Try using it first. If that fails, then use SD! or CCC.