Just to make sure there is not confusion in this thread, I think Andrew's post was about number of search results, not about search volume.
Clearly there are alternative sources, paid and some free, for search volume.
I do track, as Andrew does, search results to get how popular a term or phrase is, using the quotation marks search. It may or may not be very relevant, but one of many metrics I look at.
For me (I am in Canada and I think Google try things at different times in different markets) the quotation marks search still seems to work as it did, although some months (?) ago I noticed that Google show far fewer results than previously when one does a search without quotation marks. I presume that is an iteration of their AI for intentional search, with a focus on what their AI deems relevant to your search.
-Bob