Dou-la-la's post on this subject, which includes links to many others discussing the recall and pointing out how to use a sling safely.
Bottom line on sling safety:
Your baby sling should mimic the way you naturally hold a baby--either vertically (chest-to-chest), or diagonally (cradled in your arms). You should be able to see your baby's head and face without pulling aside the sling fabric. Your baby should not be in a curled C-position; keep your baby's airway clear by keeping its head extended, rather than tucked into its chest. See this fantastic illustration by Sleeping Baby: