In the commentary for the excellent film Ronin on DVD, director John Frankenheimer talks about the ambient light in Paris during the film's principal photography. He says (I'm paraphrasing) that he had always that thought French directors had some sort of trick for getting perfectly diffuse, bright, natural-looking light in their films shot in Paris, but when he actually shot in Paris himself, he discovered that such light often occurs naturally.
The light he's talking about is still common today, and it's hardly unique to Paris, but in Paris there are many nice things to look at and appreciate when light of this type is available. It's essentially just due to very even, thin overcasts that diffuse sunlight into an almost perfectly uniform white sky, without substantially reducing the intensity of the light. So you get a very bright, shadowless, perfectly even illumination that can be ideal for some types of photography. You may not need any artificial light at all. If you just want to light your scenes in a utilitarian, effective, and inconspicious way (as Frankenheimer would have wanted for Ronin), this sort of weather is ideal.
I like this kind of weather, too, because I don't always need sunglasses (although it can often be so bright that I wear them anyway), and there's very little unpleasant glare, since there's no direct sunlight to bounce into your eyes. It also tends to spell cool weather, which I prefer over hot weather. As for photography, sometimes it's nice (when you don't want the lighting to be noticeable), sometimes not (when you want light to be obvious, as during “magic hour”). The one drawback to this kind of overcast, diffuse light is that the brilliantly white sky tends to fool automatic exposure systems on cameras, causing everything else in an image to be reduced to a dark silhouette. Often you have to compensate for this exposure error manually.
The main thing that is nice about Paris weather, compared to the desert hellhole in which I was born and raised, is that it is highly variable without being extreme. Some days it's sunny, other days it's overcast. Sometimes it rains, sometimes it doesn't. Sometimes it's chilly, sometimes it's warm (I prefer chilly). In my original hometown, every single day of the year (with a handful of exceptions) was sunny, hot, and cloudless. That kind of invariable weather has some practical advantages, but it gets really old after a while, and when the heat is oppressive it becomes positively stressful.
Anyway, I walked around recently on one of these John-Frankenheimer days, still wearing sunglasses because the overcast was extremely thin, and I thought of his comments again. It also made me think of many video games, in which there's a kind of magic, all-around light without shadows that clearly illuminates everything; some of the games I like (The Sims, Second Life) are like this.
While walking around, I saw a bicycle tour riding on the sidewalk, which isn't strictly legal. It's usually tolerated because being on the sidewalk avoids vehicular traffic, but when you have a dozen or more people on bicycles riding on the sidewalk simultaneously, it's a substantial hazard to pedestrians. I have to wonder why the tour leader chose to do this, as it's not very safe.
Just a short time after that, I saw another tour (by the same company) on Segways, near the Invalides. Segways are legally considered pedestrians, unlike bicycles. The irony is that sometimes the tours have people riding bicycles on the sidewalks, and sometimes they have people riding Segways on the street. Oh, well … no accidents thus far, as far as I know.