I love this. It's very sleek - I didn't want a bulky car seat that would take up 1/2 of the backseat row. Very tough construction, but very soft inside. My little girl loves it! Also, the seat folds up for easier transfer from car to car or storage.
I have 3 toddlers and needed smaller profile car seats so I can fit them all in one row. That way the kids can play together, and also I am able to collapse the third row seat in my minivan to make room for luggage space for a long trip. A friend introduced me to the Diono, and based on my research, it's the only brand with thin profile to allow me to do what I need. It is not bulky like others, but yet comfortable. I am not giving it 5 stars because of the buckle which tends to be hard to lock and unlock. I bought three and all three are like that. I had to exchange the first one I bought because the buckle did not even work. As the kids grow older, I may see that as a positive so they can't unbuckle themselves. Other than that, I highly recommend it.
We've had 4 of these Diono (or Sunshine seats previously) convertible seats. Overall they do the job of fitting into skinny cars well. I don't like the clicking mechanism to tighten the straps. It's slow and doesn't seem to tighten enough. And the newest seats that we've had seem to loosen when attached to the car not using latch when I tighten the Diono belt on my son.