Miracast is not a new gizmo, it's been around longer than Chromecast has. I've tried several different Miracast adapters and haven't been impressed with them at all, Chromecast works great though.
BTW, not all devices support Miracast. If your laptop is running Win 8 or 8.1 then it supports Miracast but you still need to buy an adapter to plug into your TV. Your laptop will then use it's wifi adapter to stream video to the Miracast adapter. Video/audio tend to lag and getting the Miracast to work with the screen resolution of your laptop can be a problem.
Chromecast is far easier to use and works far more reliably.