It is painfully slow. If you have to ride Muni on at grade sections it is a complete joke. I lived for more than 10 years with my front door opening to the T and a job at Embarcadero. Straight shot on the T (this was prior to central subway opening, an event I was waiting for the entire time I lived there). It was so bananas slow and unreliable that I exclusively biked, even when raining, since it was so much faster and I actually could rely on even getting there. I gave up on it entirely pretty quickly. I felt terrible for anyone who couldn't bike who actually had to rely on that garbage system.

God forbid you have to switch lines on your surface street burdened route, good luck.

The last time I risked it and tried to T home from an event (very against my better judgement), some sort of "security incident" happened, causing them to stop and unload the entire train and keep it stopped it there blocking the tracks entirely in that direction for investigation. I walked 30 minutes home. Very fitting final ride capping my decade+ of disappointment with that pathetic excuse for a train.

Muni access was one of the selling points to move where I did, I still get depressed/pissed thinking about how terrible it actually was! There is a tiny corridor served by underground Muni which is functional, but it's such a small fraction of the whole system.