The Mini can play the majority of Blu-ray rips at 1080p with DD or DTS with Plex just fine, so long as they've had decryption and HDCP removed. Don't know about the Windows side as I only use it to rip 'em.
The only thing I could see preventing the playback would be the integrated graphics card, but even then I not sure it would be a problem. I sure there is someone that can tell the answer.
-iGrant