I picked up an Asrock J3455B-ITX motherboard and performed a bunch of tests. Here's what I've found:
When a screen is plugged in (i was using VGA), the system was very unstable - rebooting every 5-10mins. Disconnecting VGA cable and USB keyboard helped. Used serial cable to monitor boot progress.
Hardware transcoding worked in both Plex and Video station. I had 3 hardware transcoded streams (1 x video station, 2 x plex) running simultaneously without any problems. However - after a some time, hardware transcoding wouldn't work from either app until the system was restarted.
When using the 2 onboard SATA ports only, the kernel would panic and reference something about activating the AHCI_LED. Adding in a 2 port AHCI SATA card seemed to get around it (although i need to do this anyway as 2 ports isn't enough!)
Booting is pretty slow compared to 1.02b. Seems to hang at "Post init" for some time. Maybe due to the following "failed to send sync event, type resync, finish 0, interrupt 0?"
Network speeds are pretty disappointing too.
File transfer to my existing NAS (4 drive SHR array / jun loader 1.02b / DSM 6.1.7):
Whereas to the new "test" nas (4 drive RAID 0 array / jun loader 1.03b / DSM 6.2):
So for me to get a working system i need to:
Install a 2 port PCI-e SATA controller to get around the AHCI_LED panic
Switch to CSM/BIOS boot mode. Otherwise the boot process doesn't always pickup the SATA controller
Ensure no VGA cable plugged in
Ensure boot USB stick is in USB2 port (only 1 on the back, the rest are USB3)
Need to investigate the transcoding issue and try speed up the network as it's terrible