Regularly. Mostly car drivers that endangered me and other cyclists, very often driving their shitty vehicles in cycle lanes instead of the abundant car lanes.
The most aggressive ones wanted to fight me, a lot chased me, one even was handcuffed by police that happened to be nearby (getting handcuffs by police is super rare here in Germany but that guy was so over the top even for a police squad of three officers). Called the police several times and sent several of those carholes to court over endangerment.
I don't regret confronting such assholes and standing my ground at all. It even improved things in some ways because police started patrolling and controlling more often in my area after several of these rows which immensely improved road safety for cyclists. (And my numerous and constant complaints about shitty parking led to even more police activity which freed the blocked sidewalks in that area.)
Confront if you want change. It helps.