Multilane roundabouts in my part of the US are absolutely terrifying because people don't know how to use them. Accidents and close calls are amazingly common. As a result, I drive out of my way to ensure that I avoid them.
As a bicyclist, I avoid multi-lane roundabouts like my life depends on it... because it does. Utterly nightmarish experience. This is why I despair every time someone is like "let's build more roundabouts in the US!" No, what you're missing is that all our roads are already too wide and all we get are multi-lane roundabouts, which are worse than intersections. At least at an intersection, I can see that one lane of traffic is already stopped, and know that it would take at least a moment to accelerate before hitting me.
I bike as my primary transportation, and there's literally no chance that I'd dare to bike through a roundabout. Seems like a recipe for serious injury or death to me.
Fortunately, I live in one of the few US cities that really are bike-friendly, so 90% of the time I'm on a bike path that is physically separated from where cars go.
Simple roundabouts are fine.