If you intend to invest a lot of time in the Mirage until mastering it, I would not recommend you to buy it at its current development stage. There's plently of work to do on this plane until it truly leaves early access status. Razbam has already announced that a major revamp of the plane and its avionic will be delivered in May 2019 - at best, it should have been released before the end of 2018.
If the Mirage is only one of many planes you will fly, fine, you can have some fun with it, but if it's your daily driver and/or only plane (as it is in my case), you should reconsider this purchase.