let's define a few things, in terms of hassle and what's "worth it"...
rebuilding hubs can be seen as a PITA, but it's cheap and easy and quick compared to buying a new hubset and lacing them up
if you're lacing the new hubs to the old, used rims that came with your 400-level shimano hubs, that would be totally not worth it, as you won't likely build a better wheelset than what you have now
if you're lacing the new hubs to new rims, you could make yourself a great wheelset, but this would be far more expensive and more difficult than repacking/rebuilding the existing hubs
you could just buy a complete new wheelset. This would be almost zero hassle, and you can get good wheelsets cheap these days, but it's way more expensive than some new balls/grease.
me? I'd crack the old hubs open, pull em apart, see if the balls/races are badly scored, and if they look half-decent, i'd just clean everything out really good and repack with fresh grease. but then, i'm a cheapskate. most ppl think it isn't worth pulling a hub apart without putting new balls in there.