I feel that there is a positive side to no notice inspections but only with a healthy condition attached. There is surely nothing wrong with the inspection team being able to see a school how it is every day.
In our school, a team would be able to see children in situ after about half an hour after arriving in school. There would be no time to prepare a show lesson so what they saw would have an honesty and integrity that cannot be there where a school has several days to be ready.
What such an arrangement says to us as a profession is that we have to know the standard we aspire to, the standard that is expected and then hit it every day.
That leads me to the rider I have. My experience with inspection regimes is mixed. Where it works (not works best, you notice, just plain works at all) is where there is a tacit sense of partnership. Current government policy does not bode well on that score, my suspicion is that the inspection regime is as much about catching schools out and railroading them towards academies and free schools as it is taking an honest snapshot of the standard it of education it provides.
So, yes, OFSTED, inspect without notice and with rigour. However, expect something less than perfection. Ensure that you judge what you see not just what you didn't. Take into account how much stress has just been heaped upon the people you have just descended upon. And remember, we all want the same thing-the best education for the children we serve.