It let's you use eNom's name servers (pointing either to an IP address, alias or set up a redirect). The benefit is that if one later will switch to another server, this will happen in minutes instead of 24-72 hours. No need to wait for propagation.
I tried this with a site within a reseller account I have, and it works (by using the alias-version, and pointing it to my name server names).
But I still haven't made it work with mail. Has anyone in here tried it - with any reseller host?
GoDaddy has the same feature. To utilize this you need to set the name servers back to the default name servers (which will take time to propigate). After you have done this, or if you just signed up an account and it has the default name servers then there is an extra button where you can take total DNS control. It works great. And your right the propigation time is much quicker then changing name servers.