As an aside, I shall now spout heresy....
Due to exactly these issues, I would have planned my home theatre / HiFi setup differently knowing what I know now and not gone for the Oppo but spent the money on a proper Surround Sound Processor instead.
The Oppo is primarily a universal disc player, (which it does exceptionally well as a stand alone unit) with some OK but not-very-good bolt-on facilities like media player (via attached USB drives, or NAS streaming, or HTPC streaming) and USB DAC (stereo only) all with clunky interfaces and pre-amplifier functions which all work in a rudimentary way but not great. However, I hardly ever use it to spin discs now - a few movies or shows a week, as I am not a couch potato.
Most of what I use my system for is music listening, multichannel and stereo.
I have around 250 SACD/DVDA and almost 2000 CD's which I have archived to digital storage and the discs are now boxed up and stored away. I use the Oppo's clunky and non graphical interface to scroll (father than flip and browse my way) through the contents of my USB hard drive to listen to music. Admittedly the Oppo iPad app is faster and way better than the tap-tap-tap-tap-tap scroll "function" of the remote control way for doing this but on the iPhone the track titles get cut off making it hard to use.
I buy and watch Blu-ray discs but will not archive these as I rarely want to watch the same movie too frequently and the files are huge so the shiny disc is a nice compact way to store them anyway.
Today, I would choose to use my old PS3 as a competant Blu-ray (and DVD) spinner outputting fairly untouched, unsharpened, neutral video at 1080p24 and bitstreamed audio via HDMI. The PS3 is a very basic Blu-ray player, but that's what we all strive for really: - just the digital video and digital audio lifted off the disc and minimally processed and fed out via HDMI. I am 100% certain that the transport in the Oppo 105 is little better at doing this than the PS3.
I would then have a micro HTPC running JRiver Media Centre outputting my stereo and multichannel music files (and the occasional movie) via bit-perfect DSD and PCM over HDMI.
Both of these would feed a dedicated SSP (Surround Sound Processor) (basically a high-end DAC like the Oppo 105's Sabre reference chips plus full and customisable pre-amp functions plus room correction like Audyssey or Dirac Live) whose 7.1 line-outs would go to my power amps and sub.
I recognise that the HTPC and SSP would have cost me twice as much as the Oppo 105, but I think it would be a much more adaptable system. As ever, I'm finding that the one-solution-in-a-box system is a jack of all trades and master of none, albeit with a sound that I really like.
Of note, just about every post in these threads are about getting the extended features of the Oppo to work properly or to be customised as best as the limitations will let us and not about it's competent performance to handle us sticking in a Blu-Ray and getting an unprocessed HDMI video signal to the display.........