I don't have one of the PedalPower+ units sold by Peter White but I do have a PedalPower+ Super-i-Cable. Whilst I haven't had the greatest run with mine; I am waiting on my second replacement, when it is working it is working great bit of kit.

My approach is to use mine in combination with my SON 28 on my Surly Long Haul Trucker to power my Garmin Edge 800 during the day and in camp to boost charge my iPod Shuffle/Samsung Galaxy S2 phone/iPad as necessary. This was working okay on my last tour until the PedalPower+ Super-i-Cable starting playing up.

If you are interested my review of the PedalPower+ Super-i-Cable can be found at Aushiker.com and my approach to touring with an iPad at the same blog.

On the question of drag. Well my SON 28 is built into the front wheel of my touring bike. If there is any drag I am not noticing it given the bike weight etc. I also have a Shimano dynamo waiting to played with in anger on my mountain bike. That hopefully happens next week.

Regards
Andrew