as a Mac user
I feel this is a bit alarming as a Mac user.
While the iPhone supports Gmail nicely, many ISPs bundle services with Yahoo which plays nice with the iPhone as well. I would hate to see MSFT take Yahoo and somehow bastardize it to become Apple/iPhone unfreindly, whick is very possible.
More concerning is the fact that variety and competition is good. Yahoo has plusses and minuses. I like some of the free servies they provide like Yahoo Answers, Flickr, etc. I have found the entire Microsoft Live and MSN and Hotmail family to be lacking. I would always get spam, never plays nice with Firefox, Opera, etc. ( maybe it does now, I have not tried in a while).
All in all, I fear that Microsoft will try to rebrand Yahoo and steer its tarffic to a Branded product and thus hurt a lot fo what makes it tick.
As another poster stated, it makes some sense for MSFT to buy the other 5% and start a massive ad campaign. But unless Google stumbles, they have no hope. But perhaps Yahoo knows they also have no hope and this is a fast and cheap bail out to make the founders millions more and exit the game early.