Although the Windows Phone Tango 7.5 Refresh update has yet to be released officially to the general public, it is already available to some in the form of unofficial ROMs, which has been crafted out of a leaked early build of the platform. The said unofficial ROMs are tailored for the HTC HD2 and the Samsung Omnia 7, although it seems possible for other smartphones to follow suit.
What makes Tango different from the previous Windows Phone versions is that it has lower system requirements, thus allowing for cheaper WP smartphones to be made. At the same time, about 95% of all existing Windows Phone apps should work on those low spec'd smartphones running the lightweight platform version. It also brings memory management improvements, boosts the overall performance of the device, and takes care of glitches, including the SMS vulnerability that could mess up smartphones.
Those of you who are willing to try out the unofficial ROMs should check out the XDA-Developers forum for more information, but be aware that flashing one is not a task suitable for the average Joe. That said, unless you have the necessary experience, it is advisable to wait until the Windows Phone 7.5 Refresh update reaches your smartphone in its official form.