It used to be a rotary, with lights. Now it is a roundabout, without lights. And it is unquestionably better now.
When a "rotary" the main circle had two concentric lanes. And traffic entering the circle had the right of way. Traffic in the circle having the right of way is so mindbogglingly stupid it isn't worth further discussion. Anyway: concentric lanes means that to use the inside lane, you need to cross traffic twice: once to get in, and once to leave. When at all busy, the outside lane cars really have no chance at all to see signals, so changing to the outside lane, and especially crossing lanes to leave was borderline impossible.
With a "roundabout", the lanes are nested spirals. And you choose your exit when you enter, the lanes are clearly marked with overhead signs. You only cross traffic once, entering. Which means usually from a stopped position (unless there is no traffic, and then it doesn't matter). So the one question of dangerous movement you make when stopped. Leaving the circle happens automatically, as the spiral lanes leave the circle.
The rotary did have lights, but these were necessary given that design. The lightless roundabout is slightly more efferent then the signaled rotary it replaced. All the engineers and city planners were on the record that lights could return, if necessary.
Oh, did I forget to mention that the rotary was not fully operational all the time? I did.... During rush hours some of the entrance/exit options were blocked off by a commissionaire. Unless you were a taxi or a bus, you couldn't exit onto Quinpool during the afternoon rush.
As is, better than before. Safer, easier, more functional. Without the cost of lights and commissionaires (which, I grant, are pretty minimal).