so... I bought it,
It's not a full replacement for HDMI out, there is some lag and it can't be used for everything, another thing - there are some compression marks when the wifi is not 100% stable.
that said - the quality is pretty good (I'm using it right now) the lag is noticeable but bearable, I'm not sure it will be good to video/photo editing but text editing, web surfing and such are great.
you don't really need airparrpot (unless you need it special features like second screen) mirroring is working perfect.
if you like me and you have a lot of apple devices this is a very nice little thing, if not you will find it to be very short in features (it can't even play videos from usb (no usb entrance at all)