I've been on the CS3 twice a day most days since 5 January (1 hour from Waterloo to Canary Wharf on the Jubilee line on the 4 put me off using that as a regular commute).
Yup, it's slow. Yup, it's narrow. While the pedestrians mostly respect it, I've seen a mother step onto it with her child without looking. The cyclist was able to dodge around her - no traffic in the other direction - but the woman just laughed as she stepped back. I don't think she realised how serious an accident it would have been for her six year old. The junctions are all different, it's very hard to work out who has priority and the only signage I've noticed for drivers is a lit up "think bike", nothing to tell them if they should give way when turning. Excluding the full intersections with lights, all the other junctions are T-junctions, so surely the "superhighway" should have right of way, but that's only some intersections. Generally the drivers give way at all of them, which is good. Part of the path was out for a time in January (thames water, I think): they didn't close a foot path, or stop parking to create a temporary cycle lane, they just put a "cyclist dismount" sign up, which did nothing but move most cyclists onto the footpath. There's also a contraflow on the wrong side of the road, so it's not unusual for cyclists to go in it the wrong way, and makes the junction confusing (you're doing a left hand turn out of a side street, yet you have to give way to someone doing a right hand turn into it ... or do they give way to you?)
Oh, and the big confession: I didn't use it for a week in March because my attention lapsed briefly and I crossed the centre line and collide with another cyclist. I wonder how often that happens?
Maybe I should be looking at other routes?