Another vote for me as I use a GPS which is USB powered and I also tour with my iPad. I also like the option to be able to ride with my lights on during the day. If it was just to power my phone I would probably not bother and instead take a Power Traveller Mini Gorrilla or similar. Really comes down to time between recharge points.

As Rifraf said, the distances between power points can be days apart here in Australia.

Andrew