I used a hub generator coupled with an E-Werk and a small storage battery for all of my power requirements while riding the Northern Tier in 2010 -- I never plugged in. This included my camera batteries, an iPad from which I wrote a daily blog entry and my cell phone (in addition to some headlight and tail light use).

Here's the blog, if interested, which includes a complete parts list and a description of how I did the power management: http://hpscott.wordpress.com

I did this at least partly just to see if I could, and there were many times for which things would have been far easier had I just plugged in while eating at restaurants and staying in campgrounds. That said, it did indeed work.

Were I to do this over again, I'd probably use the charging equipment again, but I wouldn't be so strict about never plugging in.