I went riding in Southern California (between Newport Beach and Dana Point) last week and got a good dose of bike lanes. (I rode a rented a road bike.) For the most part, I thought the lanes worked well. I'll give them a B+.
They had lanes on the Pacific Coast Highway, which is a 55+ mph road between towns and 10-35 mph street in towns. The lanes were largely wide and clear. The biggest problem (not surprisingly) came at the intersections. The lanes just ended and dumped cyclists into right-turn-only lanes that led into gated communities. The lanes should have been run to the left of the turn lanes. There was plenty of space.
The lanes wisely ended in towns. That was needed to avoid on-street parking. Plus, there is little need for a lane when traffic toodles along at 15-25 mph.
The PCH bike lanes eventually ended entirely and were replaced by parking-permitted shoulders. Riding in those shoulders would be perilous because you would have to weave in and out of traffic, and the shoulders sometimes disappeared without notice.
I did see one stupid lane on a 25 mph side street. There was a nearly unused larking lane (it was off season), a bike lane, and a car lane. If the parking lane had been full, the bike lane would have been in the door zone. When the parking lane was empty, the cyclist was riding needlessly to the left.
Other than the one stupid 25 mph bike lanes, the bike lanes were limited to freeway-like roads. They were wide and generally well-cleared. I doubt that cities could maintain lanes in less gentle climates.
There were signs in some places that said that sidewalk cycling was allowed, but it was on wide sidewalks that few pedestrians used on freeway-like roads with few intersections. Plus, cycling was still allowed on the street. I'm not sure about the wisdom of encouraging sidewalk cycling, but my guess is that they're used mainly by pedestrian-style cyclists. As long as you ride like a pedestrian, those sidewalk routes can be safe.
Now, if I can just convince my city to limit bike lanes to high-speed (>35 mph) roads, I'll be happy.