This.
Also, if it's a roundabout on a busy street (and "busy" can even be inside a shopping center, etc.) and you are entering from a less busy side, you're screwed. I have literally sat at a roundabout for 10 minutes or so waiting for an eensy weensy opening where I had to floor it and wedge myself in and pray the person coming around with the right of way had good brakes and would use them. If it had been a stop sign intersection, I would not have had this issue. People also don't signal that they're getting out of a roundabout, so you're never quite sure. In contrast, most folks around here signal they are turning after a 4-way stop, or else I can see their hand on the wheel and know. Roundabouts just obscure part of my view.
I've never understood the blind love of the things. They are only slightly kinder than speed humps.