The majority of the time I click on the Google doodle I discover something new. I learn about people I had never known about previously. There is no negative effects of Google doodles at all. Only some one looking for something to blame would dislike Google doodles. Google > Bing
Google Doodle provides a way for the company to celebrate certain days, events and people in a subtle, but fun way. It can also be very educational for Google users who may not know about something that is taking place that should be celebrated. Millions of people use Google daily and this is a fun way to make the public aware of certain people or events.
The level of knowledge that passes for "culturally informed" these days is terribly low. Google is doing its part to keep the masses a little more knowledgeable and I applaud them for that effort. If I had my druthers, people would be required to click through the doodle and read the article before continuing on with their search.
I think it is a pretty cool thing. Not only is it unique and kind of keeps google from becoming a stagnant home page it can almost be looked at as some type of semi educational tool in order to make people aware or whatever of certain people or events.
The Google doodle icons are a waste of time. I never click on them and generally do not pay attention to them. They are a distraction and can take away from brand recognitions when the doodle is particularly abstract. They should just stick with their base logo so consumers are not confused.