I've seen roundabouts in other cities. Most of the time, they're pretty logical and easy to adapt to. Some are awfully busy and a bit more difficult to maneuver, but for the most part, they are effective. There's a new one in the city of Austin at I-35 and 51st street and judging by the video from TxDot, things are running smoothly. In case you've never seen one in action, check out the video.