I'm the guy with the last thread on the SRAM i-light. My problems were that there was a squeak, and vibration. Luckily the squeak went away, as the SRAM technical people didn't want to talk to me other than to explicitly warn that opening the hub was courting disastor.
The vibration is another story. It seems to max out at around 14 mph, slowly waning at higher speeds. It totally cuts out when I take the charger out of the circuit. This is the Busch and Muller "Ride & Charge".
Anyone have experience with this on the i-light or other (shimano? schmidt?) hubs? It's not that the vibration is all that bad (I'm usually going slower than that on tour anyway), but it's a constant reminder of energy being sucked away. Plus, it does interfere with the nice smooth ride of my stell LHT.