Honestly, I do not personally track Google at the level of looking at my raw log files daily. But a WebmasterWorld thread describes Google recently (i.e. "for months") using HEAD only requests for crawling. Typically, Google uses GET requests when crawling pages, to pull the content down to its index. Google has now been also using HEAD requests to just pull the header data.
This is possibly a method to more efficiently crawl pages. They can (1) make sure the page exists quicker and (2) they can pull the last modified date and other header type information only.
Forum discussion on this new (??) GoogleBot behavior at WebmasterWorld.