Know that you'll have to apply the protected mode fix, I would advise against the beta driver currently out because the fix doesn't work on that version, and things like the Netflix App, Hulu App and Media Center will crash/not work without protected mode audio enabled (which no Phoebus driver enables by default, thanks Asus). Use the driver from search under Asus Support:
http://www.service.asus.com/#!Downloads/c1wax (Type in "Xonar Phoebus".
Know that over a month ago I submitted a bug report of that on beta, and also the firmware update not working on beta...neither of which have been answered since... I can confirm once you download the regular driver and enable protected mode audio, the card works just fine.
If you use Netflix, launch it and try to play something, it should point you to the Microsoft Protected-mode audio fix. Otherwise, search for it on the web and make sure it's from Microsoft, download and run it. Good luck!
*Add-in, a little side review of Windows 8 since that's the topic here: Windows 8 is nice, it IS the future of Operating Systems, a much more streamlined controllable interface. We've been using the same start bar for 17 years while hardware has advanced massively. With that said, there are quirks and big ones. The biggest of which, being an IT Pro I have issue with, is the recovery/auto fix options. Unlike 7, there is no built-in recovery on the HDD, you will have to use your dvd (so make sure you have it handy). Auto-recovery also almost never works, the internet is ridden with complaints of it, you are better off dropping to command prompt and attempting to fix the issue yourself. As far as dealing with something out of the norm (a lost file, corruption, etc) Windows 7 wrecks Windows 8, and that's important to me in keeping my computer 100% because I'm always changing hardware, messing with settings, etc. I've gone back to Windows 7 x64 Ultimate from Windows 8 Pro/Media Center.
Asus G20CB - Core i7 6700, Nvidia GTX980, 16GB Ram, 256GB SK Hynix SSD, 1TB Samsung SSD.