When my Mom got her new bike, she wasn't really interested in changing the appearance of her bike with reflective film, until she got caught out after dark. I cut strips of 3M Scotchlight (the white (applied to the frame)) and Avery's Retro Reflective films (the black (applied to the fenders)), and used Lightweights for wheels on her spokes.
After application of the films, the changes are barely noticeable.
Close in photo with flash after dark
Distant photo with flash after dark
Compare that to my bikes (where I was less concerned with altering the appearance of the bike).
Giant Rainier 2004 and GT Transeo 1.0 2008
For more info, check out
this thread on BikePortland.