44.6B is a lot of cash, and they didn't even need to go to the bank. That's nice.
Google is the big winner here, me thinks. Yahoo proves that they could not solve their problems, and Microsoft admits that they cannot leverage the brains they have on the payroll (I believe Microsoft to be second best in terms of brain-per-sq-feet, only to be bested by IBM) to produce a viable product in the search wars.
The value proposed is too big not to provoke something to happen: the deal is most likely to go forward, and only a Yahoo + Google scenario (and we can imagine how happy that would make the Y! board) could save Yahoo from falling into Microsoft hands.
The next months are interesting because Microsoft will unveil his plans of assimilation to the horde of Yahoo workers, and if those plans include migrations to Microsoft technology (remember the HotMail purchase? We can only hope that Microsoft did learn a lesson there), then the natives will be restless. Probably a mass defection to Google, and other smaller companies, and a rush of new startups.
I personally don't have big concerns about this merger. There are a lot of tools that I use that belong to Yahoo (Flickr is probably the most important, other smaller software tools like Firebug, YSlow, the standard CSS layouts, also made the list), but I think they will survive just fine.
In terms of the Instant Messaging world, two giants that where already sleeping together are getting married. I do feel sorry for this, because although I don't expect to see an official XMPP gateway from MSN, I was expecting to see one from Yahoo in a year or so. I do think that AOL will probably align with the XMPP federation now. They really don't have nothing to loose now.
Next episode: the Yahoo board response.
Update 2: tied for first place, Fake Steve Jobs take on Microsoft/Yahoo deal.