Microsoft (Nasdaq: MSFT) is finally getting serious about mobile.

I'm bullish on Windows 8's mobile future, and Windows Phone 7 is getting a much-needed update to 7.5 "Mango," which officially began rolling out yesterday. The update includes important features such as multitasking, deeper social networking integration, and tethering/hot-spot capabilities.

I call it much-needed because Microsoft has a habit of being fashionably late to parties, particularly those of the mobile variety, when compared to hosts Apple (Nasdaq: AAPL) and Google (Nasdaq: GOOG), which have been charging forward with their own respective operating systems. Apple's iOS 5 is due out alongside the iPhone 5, which is rumored to be unveiled Tuesday. Android's next dessert iteration, Ice Cream Sandwich, is also set for an October or November release.

Both of those dominant operating systems are more mature and advanced compared to Windows Phone 7, so Mr. Softy has some ground to make up. Some of Mango's "new" features are just playing catch-up while others are just plain taken for granted nowadays, like visual voice mail. On the other hand, some of its attributes differentiate the OS in welcome ways, like the dynamic live tiles that third-party developers can now utilize and the overall "Metro" design style.

Even though Windows Phone 7 is still a laggard in terms of market share, I think the platform has decent prospects at getting comfortable in third place for the long run at the expense of Research In Motion (Nasdaq: RIMM), which is doomed without divine intervention. I don't think it will ever come close to overtaking iOS, but the mobile smartphone market is growing so quickly that third place isn't such a bad position.

The bottom line is that now any sentence containing "Microsoft" and "mobile" is not necessarily a joke anymore. If Windows Phone 7 can continue to get aggressive and timely updates, it will be up to speed in no time. Windows 8 and Windows Phone 7 seem more on track now to be a dynamic duo, like Mac OS X and iOS. I can't quite say I'm bullish on Microsoft overall just yet, and the primary thing holding me back starts with a "B" and rhymes with "calmer."