It's ridiculous that Address Book does such a bad job of printing labels. This little app mostly fills the bill. Be sure to read the "read me" file so that you understand how to load the Avery templates.
My only quibbles are that the font sizes seem to come out on the labels much larger than they should for some reason (an Ariel 10 looks more like an Ariel 12) and that there doesn't seem to be a way to fine-tune line-spacing. Also, printing seems slow from this app. But hey, the program's free and it works!