They use a sealed ball bearing assembly that doesn't need a preload/end play adjustment or cleaning and packing with a good wheel bearing grease,
Worth it - IMO - NO. The OEM tapered roller bearing is a superior bearing to the sealed ball bearing. After all servicing the axle bearings isn't something that you do every day. Maybe once in a cars life time. No big deal.
http://www.moparts.org/Tech/Archive/axle/12.html

Clean it, if it's Dirty. Oil it, if it Squeaks. But: Don't fix it, if it Works!