I've been running a Shimano dynamo hub on my commuter/touring bike for five years. My estimate would be that there's about 15,000 miles on my front wheel. My light has actually not been working for a couple of months, and I've been lazy about diagnosing it, but I did make one attempt, and I'm 90% the problem lies somewhere in the wiring between the hub and the light. My little current tester has to problem detecting electricity from the hub, but the light isn't coming on (but it would come on when it was on the stand, while I was doing the trouble-shooting). Point being, that unless I learn otherwise when I finally sort out this issue, I'm fairly certain that my Shimano hub has been problem-free, well worth what I paid for it, and has lasted at least the 5 years that the SON is warranteed for.
If I had money to burn, I'd get a SON, because I hear great things. Since I do not, I would not hesitate to get another Shimano hub.