I feel so low tech. I put these on my commuter bike ( http://www.rei.com/product/808967/li...wer-reflectors ) and then thought them so useful yet unobtrusive that I put them on my touring bike, too. In normal sunshine you can't see them, but they light up beautifully when they need to. I've been surprised at the number of positive comments I get for them from roadies...ok, not weight weenie roadies, but people who spend a lot of time on their bikes.
Note: you're really paying for the application method. The reflective tape is very thin (think saran wrap) but it comes cut on these tiny little cards that are perfect for just wrapping around the spokes.
2009 Waterford RS-14 S&S Couplers - Brooks B68-Anatomica - Traveller
2008 Waterford RS-33 - Brooks B68-Anatomica - Go Fast
2012 Waterford Commuter - Brooks B68-Anatomica - 3.5-Season/Commuter
2011 Surly Troll - Brooks B68 Imperial - Snow Beast