Jennifer Berry says that at the UGA bee lab, they feed pretty much exclusively with baggie feeders - put a ziploc filled with sugar syrup flat on top of the frames, surround the baggie with a shim or an empty box, cut a slit in the top of the filled baggie and close up the hive.
The only disadvantage is the environmental one of not being able to reuse the baggie, thus contributing to the growing pile of plastic waste in the world. (And if the baggie is not flat on the tops of the frames, bees can get in and drown).
Linda T in Atlanta (who doesn't follow Jennifer's wise advice all the time and sometimes uses Boardman's to her deep regret!)