Netgear support over the days following my report of the problems I was having with the RN104 was awesome. They tried everything, kept me informed at all stages and eventually asked me to return the old one and get a replacement.
The replacement now has an uptime of 26 days and hasn't skipped a beat.
Moral: don't generalise based on a sample of one. (Of course I could quibble about how the faulty unit got past QA in the first place...)