Apple TV does output LPCM.I have purchased alot of MiniDSP products over the years and here are my concerns:
1) it's using the same DSP chip as the Flex with 4 outputs, which is the same DSP chip in the 2x4 HD, so don't expect miracles in terms of processing. this is incredibly disappointing
2) It will not be competetively priced, If this thing is not significantly cheaper (without Dirac) than the Denon X3800 (or the X2800 for that matter) then I don't think anyone should be interested.
3) You might not be able to program the device to advertise itself as 2.0, 5.1 or 7.1 capable, and since it's not capable of downmixing or upmixing this might ruin the experience for anyone with a setup smaller than 7.1.
4) There is no way to test whether your TV is going to work as intended as a decoder, that means you need too buy from a local reseller with a very generous return policy.
5) 8 outputs is a little on the low side for me, I kind of like to aim at minium 9 outputs so you get to choose between 5.4 or 7.2.
6) No promises (or outputs) to support DLBC in the future.
7) the Apple TV does not support LPCM output and it's the biggest provider of multichannel music at the moment (there is nothing else to be honest), which makes point number 4 even more problematic.
Unless you're a gamer looking to get the audio processing out of the PC and include your consoles while you're at it and don't want to deal with a bulky AVR then I don't see this product working perfectly for you without some sort of compromise.