Support for streaming media from your Windows devices to other DLNA and "PlayTo" media devices (like TVs, Stereo Systems, XBOXes, PS3s, Windows Media Extender devices, and even TVs) can be found in Windows Media Center and Media Player, and even quite a few Windows Phone devices (the vendor generally has to provide support on such a low-power device, but for example Nokia and LG have DLNA-capable apps).
I will agree getting all of your apple devices to play together is easy, but so is getting all of your Microsoft-centric devices to do so is also easy. Going for the mixed-mode is where Apple requires 3rd party software (at the least), whereas Microsoft Windows, Home Server, and even some Windows Phones do this as well out of the box.
Use what works for you, of course, but vendor lock-in isn't usually a good thing if you ever want to change in the future.