I have Sony W70B TV with miracast support (I can confirm that as i have other devices that support casting and it has worked with it) and a Sony Vaio Fit 15 Laptop with Series 7 Chipset and miracast support as per OEM (SONY). On windows 8 I was able to stream at first but then it stopped working. In windows 8.1 It didn't showed option for miracast/wireless display anywhere in the os. Now I have windows 10 Technical Preview which shows my TV as an option in the Win+P menu as well as in settings. It also shows successfully installed drivers for device but it never connects properly. When selected it tries to reinstall drivers and passes but it never really casts. sometimes it shows a blank screen or it shows Screen mirroring failed.
P.S. I have tried this tv with other laptop of mine and it connects successfully. Also, this laptops connects to an other Miracast Support TV i have "sometimes" successfully. (Before disconnecting after a few seconds on both devices)