My thinking is that you might as well have a fluorescent waterproof, as murky rainy daylight is when it's most likely to be of any use. The rest of the time, I don't think it's of significant benefit. Retroreflectives are a good thing, but mainly on the feet/ankles/lower legs where they're in motion and on the hands/wrists (for indicating). For everything else, there's frikkin' lasers and/or perfectly good daylight.
The being-seen-through-a-wet-side-window-by-a-driver-about-to-pull-out-of-a-juntion scenario is one of the trickier edge-cases of bicycle visability. Reflectives won't help, as the car's lights won't point at you until too late. A fluorescent jacket may be of some benefit in the right kind of murky gloom, but not darkness or under street lighting. A nice bright front light is clearly the most important thing, but can blend into the background. Much as I hate flashing front lights, this is one situation where they seem like a good idea, at least as a secondary to a proper static light, as they unambiguously scream "BIKE! (or distant police car or something)".
But at the end of the day, it's the driver's responsibility to look before pulling out. If that means wiping/opening the side window, or squirming around in the seat to see round the pointlessly chunky A pillar, then so be it.