no not google business listing.... Aggregate Review Schema, Stars in the Search Results for Local Businesses
In my point of view its not effective anymore. I found few sites has good rating but still struggling for rank. So, I think now-a-days its not a big deal anymore.
I think it’s important. I don’t say it’s a direct SEO factor. But when the user sees rating stars, he will click it with higher probability. So your click through rate will improve and it will effect overall SEO.
Agreed, its still important for better click-through rate, and thus customer conversions. It catches people's eyes.