I did not try any ...factory.bin image for a while. These were systematically non-functional back in May-June this year. No idea about the current status of factory images.
I did try sysupgrade images recently less then 2 weeks ago. Both Chaos Calmer 15.05 RC3 and the trunk were not truly working solutions. Camera boots these images, but cannot properly activate the overlay filesystem due to size limitations.
However, I believe the trunk image was 3670020 bytes when I downloaded it, but the current one is just 3407876 bytes. This could be a critical improvement!
I made several attempts to compile customized image from CC 15.05 and the trunk myself. I managed to build working image with proper /overlay and all the networking bells and whistles but faced a strange problem with mjpg_streamer - it failed with "Trace/breakpoint trap" error message every time I tried input_uvc.so as an input.
Finally, I gave up trying and fall back to self-built r45924 with ldpinney's patch.
I have now working mjpg_streamer and motion. I cannot send emails with images as I do not have space for this functionality. I did not try audio functionality.