Stockholm Bike Fashion: The "fixie" craze has yet to hit Stockholm the way it has in the US. If you have a single-speed, it's an standard* steel-frame, coaster-brake style. Other "standards" are three-speeds. (I would call an "standard" an "old person's bike" except that young people who are not bike enthusiasts ride them too. So they are just "standard".) Enthusiast bikes are derailleur-equipped late-model mountain bikes or road bikes with bright paint jobs. (I did see one Rohloff-equipped bike. Nice.) I saw aluminum, not carbon, frames in the display windows of the one bike shop I stopped at. As for couture, I saw only a few people wearing Spandex, and they were all club riders. For that matter, I was remarkable (even in my street clothes) for wearing gloves.
Infrastructure / Pedestrians: Bikeways, where they are uninterrupted, are great, e.g. along a waterfront, especially where there is some separation (other than a line of paint) from pedestrians. But they are always problematic where they end, or have to deal with intersections, or cross roads. There is a lot of "engineering" (signalization, signage, and control) involved. And the cyclist always has the option of using the roadway anyway. Just as in the US, delivery trucks and cars park in the bikeways, forcing the cyclist into the motorway. The adjacency of bikeways to pedestrian areas is problematic, I think bikes (moving at 10-20 mph) belong more with cars than with pedestrians. I found myself using my bell a lot.