Some background info first:
A while back, I switched to PBO's IMS-DEMO firmware because it was the only one (official, beta, or custom) that supported simultaneous HDMI and SPDIF audio output (a supposed "glitch" which PBO eliminated in later firmwares), which was very important to me.
My PBO has an internal HDD and is hard wired to my network. I use the PBO only to watch movies, mostly Blu-Rays. I use MakeMKV (great program!) on my PC to convert the main movie file to an MKV directly onto the PBO HDD.
I decided to try the new patched medeBO and ACRBO firmwares available here. Both offer the simultaneous audio output I need, and are far more attractive and user-friendly, especially the medeBO firmware, which I thought would be a keeper.
Unfortunately, both patched firmwares have VERY slow transfer speeds. I used MakeMKV to make an MKV file of "North by Northwest" from my Blu-Ray (yielding a 31.9 GB file). With the IMS-DEMO firmware, the entire task was completed in 77 minutes with read speeds in the 1.8-2.4x range. With each of the two patched firmwares, transfer speeds for the exact same movie conversion was in the range of 0.4-0.1x range - I aborted each attempt after an hour when it became clear that this would be a 6-8 hour task.
I'm back with IMS-DEMO. I really liked the mede8er firmware, and maybe this will be fixed eventually.