Some people have reported alignment problems when printing -- usually they say the cards overlap vertically. We've found the best solution is to make sure Adobe Acrobat isn't resizing the image. There are different versions of Acrobat, but the instructions below should guide you in the correct direction.
Once you're looking at the image of the cards in Acrobat:
That's it. You should be ok to print now, though you still might want to consider printing a test sheet on regular paper first if you're going to use Avery's Business Card Sheets.