While some people are voicing their disapproval, I think this is more than enough on Google's side. It seems ridiculous to assume a for-profit company that has to answer to shareholders would shut down completely for the day, however the fact that both their homepage as well as the logo on all search result pages link to a detailed explanation that your average user should understand is more than enough. We should be applauding this action and hope that it spreads the word even further.
Edit: Also for those concerned that the Google Doodle isn't enough; here were stats from Wikipedia on a Google Doodle search query: http://stats.grok.se/en/201109/Albert_Szent-Gy%C3%B6rgyi - I believe 4.2 million views is significant.
Edit 2: And a HN discussion on click-thru rates for the Google Doodle topic searches: http://news.ycombinator.com/item?id=3004392