The Starlines we've bought are generally good producers. My grandfather has averaged 60 lbs.per hive over the years in an average location in central Iowa. His main interest was for pollination of his garden, so he wanted a gentle bee. They can overwinter well, and don't eat themselves out of house and home like some of the agressive Italians. Their best feature in my mind is their gentleness.
Now for the down sides: They they collect a lot of propolis, which can make seperating supers a little more difficult, and clean-up of frames/supers takes a little longer. The queens I have had are not as easily spotted as some other races due to the overall smaller size. If you get a Starline I would recommend getting the queen marked. Now for the worst downfall. Not many producers carry Starlines, and if you need a queen shipped ASAP kyou might be out of luck most of the year.