The dangers of using a legal cycle lane for passing slow motorized traffic include:
Vehicles turning left without warning across the lane.
Vehicles turning right, with or without warning, across both lanes, without visibility of you.
Pedestrians crossing between cars onto the bike lane.
Taxi and car doors opening.
Given the potential for danger, you should ride at a speed where you can react to dangers, and think ahead to predict possible conflicts, ie be a good rider, not a bad rider.
Vehicles turning left without warning across the lane.
Vehicles turning right, with or without warning, across both lanes, without visibility of you.
Pedestrians crossing between cars onto the bike lane.
Taxi and car doors opening.
Given the potential for danger, you should ride at a speed where you can react to dangers, and think ahead to predict possible conflicts, ie be a good rider, not a bad rider.