I had a pair on my commuter for a few months, so I'll give some comments based on that. Just to put things in perspective - I ride an older, steel 3-speed and weight/drag issues being brought up in the context of utility devices like these kind of annoy me - if you're a racer, the only people where weight/drag should be an issue you obviously aren't going to be using something like this.

The set I have is one with the capacitor, so they stay lit at lights. Also, I haven't noticed any fading or flickering when I slow down, probably because of the capacitors. The lights are pretty bright, comparable to a blinky. My only issue with them is that because of the way my fenders (original metal ones) attach I had a hard time positioning the lights, especially the rear, so they didn't aim as far up as I would have liked for visibility.

Are they good enough to be a sole light source, no. What I like them for is a vehicle-side light that shows where you are in the road. Since most of my riding is next to traffic with people who aren't used to bikes on the road (not many B'more cyclists) having extra lighting on the car side of the bike is great.

I did not notice any drag or spoke issues. It's possible there is some, but the magnet involved is only slightly more powerful than the ones used for bike computer sensors so unless those thrown you out of whack there shouldn't be a big issue. The only reason I'm not using them currently is I got new wheels built up around a dynohub and I haven't bothered to put the Reelights back on. I'm debating holding them off for the touring bike I'm getting built since it would be nice to have lights on it that I don't need to think about charging or changing batteries in for touring.

If you have questions feel free to PM me. One thing that has always irked me a bit on these boards (all of them, not just A&S) is the regular occurrence of people rendering judgment without firsthand knowledge, so I'm willing to answer any questions about these from the position of someone who has used them.