I think it's mostly firmware. The series of issues, including current ones, are very similar to the issues customers experienced with Bell 9200s and 9242s when they were first released. The firmware is still under development. New features, like the external drive, add new bugs and they are not done yet. Bell's PVRs got quite reliable a couple of years after they stopped adding new features.
As far as the hardware is concerned, the 630 is no worse than any other proprietary BDU hardware out there. If anything, it should be better because it's a generation or two newer than the competition is using. These things are programmed at a fairly low level and it can take some time to shake the bugs out of the custom firmware and the operating system (usually a port of embedded Linux) that it's running on. A bug in a driver at the O/S level can be difficult and time consuming to fix. Good talent that can do that type of programming is difficult to find. You would think that Motorola would have the the people but the company has been going downhill for some time and the most talented people are usually the first to leave.