I can't really say which one is number 1, but there's 2 major issues.
1) Proper formatting of the drives. I suspect a LOT of the slow speeds of the device are actually because, for whatever reason, the disks don't get properly formatted. When I did an upgrade to 2TB drives from a pair of 1TB, I was only able to transfer at about 13MB/sec across a gigabit network. When I tried dropping the drives into an enclosure and running the pull from a Linux machine, it was only able to grab it at about the same speed. Yet after I was done, I reformatted the drives to test for speed, and under ext4 on the same machine they were able to pull and push at 30MB/sec through USB. That suggests that the slow speeds are because of improper formatting.
2) DLNA that actually works. For some reason, the device will no longer show up on my PS3, and I've never been able to pull it up as a media server on my Win7 machine, instead having to just use it to load the files as standard.