Well, I've given up on my 120W Kensington power supply. I got it after having seen a number of other road warriors use it, but it just does not hold up. Sure,it works fine on normal wall-supplied AC current, but typically when I travel the AC or DC current is not as clean and the Kensington all-too-often fails to work.
For example, when I take a cruise the supply usually fails to work when we're at sea (when the ship's electric motors induce noise on the cabin power-line). When I fly, over half the time the supply fails to charge the laptop when plugged into the DC or AC seat outlet (again, I expect because of dirty AC power). I suspect that the charger is trying to protect the laptop. That's good, but it really needs to figure out how to filter out the noise and move the clean DC power to the laptop. Because the charger failed on my last overseas flight, I could not work on the plane. As a result, when I arrived in London with a dead laptop I got stuck in immigration because I could not pull up some vital information from my laptop.
Yes, the charger is light, small, and easy to pack but the (very) short AC cord can be a PIA. The DC cable is also kinda fragile so it's best not to stress the connectors or twist it when packing it away. I would have given up earlier but Kensington has already replaced the failing units twice before. Unfortunately, I'm not cruising or flying that often so it usually takes some time before I discover the unit is not working. At this point I know I needed a replacement. Unfortunately, Kensington won't replace it again, so I think we're done.
When shopping for a replacement, I notice that the Lenovo 90W AC/DC charger is Kensington's old model (that supports a Y cable to charge two devices at once) so I don't really want to go there. Kensington supports a 2-year warranty but, twice burned, once shy so I'm still looking for a good, reliable AC/DC solution. Perhaps a good 90W inverter makes sense... The problem is, I'll also need to carry an AC brick as well 'cause the Kensington failed when connected to the AC on the 737 Seattle/Chicago leg.
My advice: Stay away from this power supply. While Kensington's customer support is great, their power supplies are not really up the the challenges of dirty AC or DC power.