I got a couple of these cheap on flea-bay, they work well and the adapter is tight in the cig outlet that I installed on my Tuono, no worries of that vibrating out. Gives you a second USB outlet which comes in handy.
I have one like this that would wiggle out of contact so I made it tighter with a little safety tape, but I would prefer a powerlet plug if it were available just because of the way it locks into place.
As I was writing this I got an email from powerlet:
"We've got a Powerlet to USB in development right now. I've got a prototype in my hand that I need to start tests on. Production will soon follow, but don't hold your breath."
I told him I'll be a beta tester.
I've gone through 3 of these Griffin dual USB plugs so far. They are very handy but not very reliable, and short run from the positive plug to the extended rim is a problem with Powerlet cigarette lighter sockets. It's basically too short to fully seat in the Powerlet socket. Even in my car the Griffin's eventually provide unstable power. Luckily I came across this problem in a short trip last fall so I was ready with a backup before leaving on the summer trip.
Also I would be careful of those Powerlet USB plugs. Somehow I ended up winning one of those (without ever having entered a contest) and though its nice that it has a light showing you when you've got power (conspicuously absent from the Griffin) the construction is pretty lame. In typical fashion, the positive contact is on a spring, and retained with a cheap aluminum sleeve that screws onto the plastic body. That cap came off on the trip to Oregon and once inside I could see that the plastic form was rough and interfered with the spring's ability to expand fully.
In summary - I brought along a few extra USB sockets in case of failure and was glad I did. I would recommend any plug have an LED to show that you have power there - a very handy troubleshooting item. Of course the USB plug is a poor electrical connection with no retaining feature and eventually the male plugs on your device cable wear and you end up with sketchy connections.