I also have a BDP-105 and have asked myself the same question.
It has so much flexibility, I find it hard to part with.
I primarily use it as a DAC for USB from Roon. It performs the 2nd Tidal unfold and also works well with Qobuz. I connect it to my AR REF5 with a nice XLR cable and the sound is excellent.
For those of you who have replaced the Oppo DAC, I’d like to hear how far you had to go to improve the sound. PLEASE LET ME KNOW WHAT YOU THINK !
I use the 2nd USB for a drive to play my DSD files natively. Roon will not do this.
Sometimes I use the Preamp HT bypass when I want to control volume from the preamp only. This works well and I can only hear minor differences driving my amp directly from the Oppo. So I can use it as a complete 2ch digital preamp. I could live with this if it weren’t for the need to play vinyl which I do often, thus the need for the AR preamp. which sounds wonderful.
I also use both HDMI inputs - 1 for cable box and one for Roku so I can play video in stereo. I like it! I just have a small flat screen mounted above speakers so it doesn’t seem to interfere with imaging.
It’s nice to have toslink and coax, inputs and outputs, for occasional use.
I also have an Esoteric DV50 that I love for CD and find it hard to part with as well but the Oppo is still quite nice and I could use it if I sold the Esoteric.
The Oppo is a unique hi performance swiss army knife. There are few options. I just saw an ad for a new Technics SL-G700 ($3000). It’s probably close in performance with updated technology...covers most of the Oppo functionality but no HDMI.