Very pleased at this point, Andy, and so far they are exceeding all my expectations, so I am labeling them a "success"!
I didn't expect them to be *so* visible at night. One of my prime motivators in getting them was to increase visibility from oblique angles. They surely do that, and are highly visible from just off-center to a light approaching from front or rear.
Also, nice as the reflective sidewall strips on Schwalbe's tires are, they can be worn away quickly by abrasive surfaces. As we toured the Netherlands' sand roads, my riding partner's tires lost their reflective stripes in a day's use, churning through the soft sand. I will be using my bike in desert playa and figure a similar fate could befall them. The spoke reflectors are above the rim, and so are not subject to the same grinding and abrasion as the tire sidewalls and should remain reflective for a long time.
Some of my front reflectors were loose, and MartinF's suggestion of a small strip of electrical tape between the reflector and spoke solved the problem. Curiously, none of the reflectors were a loose fit on the rear wheel's spokes.
The retro-reflective effect is nearly identical in brilliance and reflectivity to the 3M Scotchlite patches on Ortlieb bags. I initially experimented with just a pair of reflectors per wheel, thinking the "bobbing" effect might be more eye-catching to a driver, but this is trumped wholly by the far greater reflective area achieved by fitting a reflector to *all* spokes. When the wheel turns, it makes an 8cm wide band of silver-white reflected light all the way 'round the wheel. They're truly lightweight and are evenly distributed, so there is no imbalance as a result of fitting them.
I've made some unfortunate purchases in the last 6 months or so that I regret; not so these. A really solid product so far. Long-term, they may wear or become dim, but for now...outstanding, in my opinion.
One last thought in closing: I got the matte black bike thinking it would help me blend in while wild-camping at night. That is still true in the absence of light shown on the spoke reflectors, and a real bonus. I had thought about removing them before my big tour, but have since reconsidered. A popular sport in some desert areas (like the Central Oregon Sand Dunes, where there isn't much to hit:
http://en.wikipedia.org/wiki/Christmas_Valley_Sand_Dunes *) is for four-wheel-drive enthusiasts to head out cross-country, bashing through sand, sagebrush, and whatever off-road day...and night. I'm thinking if the bike is propped upright on its Click-Stand and every spoke is reflectorized, it just might catch the eye of a nighttime off-roader before he would otherwise flatten the tent and me in it. In that circumstance, I'd be grateful for every stray lumen they reflect. That's the one instance I'd really hope someone *did* discover my stealth camp.
Yep, at this point, "Danneaux-recommended".
Best,
Dan. (*...who thinks the Lost Forest is an interesting place as well:
http://en.wikipedia.org/wiki/Lost_Forest_Research_Natural_Area )