These days, a mobile OS is only as good as its ecosystem, and no company knows this fact more than Microsoft. Its smartphone platform known as Windows Phone has had plenty of growing pains during the first three years of existence, which is mainly related to a limited number of big apps and game titles. Despite these struggles, Microsoft has slowly but surely been able to court heavy-hitting developers -- even if only one or two at a time. Today, however, a gaping hole in the Windows Phone Store will be plugged, as Instagram will be available as a free download beginning today around 2pm ET.

The Instagram app, which will be available only for Windows Phone 8 (sorry, legacy users), will offer Live Tiles that refresh with new data on the Start screen, and will also come with support for fast-resume; sadly, there are quite a few features that won't be available right away, such as video capture and uploading, photo tagging, viewing geotaxis and -- arguably the most important -- in-app image capture . Instagram explains that it wanted to get the app out to users as quickly as possible, so a few features had to be left out of the first version (which Instagram is calling a beta), but it assures us that future updates will come with plenty more functionality (as updates are often wont to do). Still, the addition of official support by Instagram is a good indicator of health for Windows Phone.

Update: Despite Microsoft's and Instagram's repeated assurance that in-app image capture would not be available, it appears that it's actually included in the official app after all. Pressing the camera button takes you into the camera roll by default, but choosing the camera icon allows you to take a pic. Once you take the image, it auto-selects that shot and lets you upload it through Instagram.

Updated headline to reflect image capture capabilities.