Evidence from incoming business and social mail during 2009 was that most of the new stamps came from booklets. And local post office branches were still using pre-security PIP stamps (especially 2nd Large, and 1st small) well into 2010.
Looking at similar mail this year - now that all the 2011 stamps from main sources have appeared - it is evident that many more counter sheet stamps are being used. This includes 1st class despite the vast number of 1st class special stamps available.
For collectors of modern postal history - stamps on cover doing the right job - use of some versions of the 2009 stamps (the ones with no year code) in 2009 and early 2010 may be quite hard to find, especially the counter sheet versions. I don't get many Large Letters with single LL stamps on, but I would say that 2009 counter sheets, and 2nd class 2010 business sheets will be difficult to find. So far only one printing date for the latter has been discovered!
What's your experience? Let us know by leaving a comment!