Microsoft sees 2012 as a year of rebirth. And so on Thursday it unveiled its first new logo since 1987. From the Microsoft blog: 
"The Microsoft brand is about much more than logos or product names. We are lucky to play a role in the lives of more than a billion people every day. The ways people experience our products are our most important “brand impressions.” That’s why the new Microsoft logo takes its inspiration from our product design principles while drawing upon the heritage of our brand values, fonts and colors.
The logo has two components: the logotype and the symbol. For the logotype, we are using the Segoe font which is the same font we use in our products as well as our marketing communications. The symbol is important in a world of digital motion. The symbol's squares of color are intended to express the company's diverse portfolio of products."
It's hard to find much wrong with the new mark. It's pleasing to the eye, simple and uncluttered, and doesn't have any onerous symbolic meaning weighing it down, à la the new Twitter logo.  It should do very well for the company. It even looks great small, which is how it's used, to impressive effect, atop Microsoft.com. 
The old logo, by the way, was designed by Scott Baker and was known informally as the "Pac-Man Logo." At its introduction, Baker said the logo, "in Helvetica italic typeface, has a slash between the o and s to emphasize the 'soft' part of the name and convey motion and speed." And now it's dead.
Of course, if we're going to look backward, nothing can top the sheer groovy brilliance of the original Microsoft logo  from 1975.
Check out Microsoft's video introducing the new logo here: