As promised, Windows Phone 7.5 will start rolling out to existing handsets starting today, capping off a journey that began back in February when Microsoft first teased milestone features like multitasking and IE9 integration at its Mobile World Congress press conference. The company remains tight-lipped about exact details of how the updates will be distributed — we don’t know which devices will receive the update in what order, for instance — but we do know that it’ll be conducted on a rolling basis, meaning not everyone will receive it at once. That’s a low-risk strategy that has worked pretty well for the Android camp so far, and after a few speed bumps during the NoDo rollout earlier this year, we don’t blame Microsoft for taking the safe route. For what it’s worth, you can track update status by carrier at a very high level on Microsoft’s site, but it won’t give you specific detail on the hour (or day) when it’s going to hit your phone.

As before, the updates are strictly cabled — you won’t be able to update to Mango over the air, though you’ll be notified with a pop-up message on your phone so that you know that you can rush back to your PC to get the goods. Both the Windows-based Zune client and Microsoft’s Windows Phone 7 Connector for Mac can be used to perform the upgrade.

My lengthy preview of Mango from June covers all the bases of what Windows Phone 7.5 brings to the table; there’s very little about the software I wrote then that’s no longer accurate. At that time, the platform was essentially feature-complete and I didn’t find any glaring bugs, so there are just a few important changes and additions that we’ll cover here — and apps designed with Mango in mind have started to trickle into the Marketplace, too. Read on.