This is a bit off-topic since this thread is listed in the "Mountain Lion Desktop Guides" section. If someone has recommendations on where this info would be more appropriate, let me know.
I just installed OS X 10.10 Yosemite on my CustoMac Mini 2012. The setup was surprisingly easy.
- HDMI Audio works; PCM output or encoded output (with an app that supports that, such as VLC or EyeTV).
- Manual sleep and auto sleep work perfectly.
- The "onboard" bluetooth works, although pairing process can be spotty. The pairing either works perfectly or freezes the system. But once it is done, it is done for good. Rebooting / wake from sleep does not require re-pairing devices like some versions of Mavericks did.
- Onboard ethernet works great (only tried with one of the two ports)
- [edit: 1080i and 720p now display fine. For now.] HDMI video out works; only tried the bottom port (the one that works with HDMI audio output). 1080p output is fine. 1080i is still crap (only the top half of the screen is visible, and vertically stretched). 720p is also garbage, in a similar fashion. This is with a i3 3225 CPU (HD4000).
- Still can't view movie trailers in iTunes. I never really investigated how to fix this.
I downloaded the DSDT file for the H77N-Wifi from the database, Unibeast and Multibeast. I followed the general instructions here:
http://www.tonymacx86.com/445-unibeast-install-os-x-yosemite-any-supported-intel-based-pc.html
I copied the DSDT file to my desktop and renamed it to DSDT.aml. At the MultiBeast step, I picked User DSDT, then selected the DSDT.aml file from my desktop when prompted. In the audio section I turned of the option for Realtek ALC892 and also enabled the HD4000 HDMI audio option. I had to pick a network driver else I lost network after the Multicast setup. I attached my Multibeast settings to this post; you can load them in MultiBeast, pick the DSDT file and then browse to see what exactly I used.