NDS Organizational Units

In Netware, you can assign rights to an OU which is by far the easiest way to assign a default set of rights to all users, OR you can assign rights to groups. AD will NOT allow you to assign rights to OU's, everything must be done with groups only. Another major difference is in the way that rights are cascaded down. If you change the rights in a Netware container, only the container object is modified. If you change group rights to an Active directory OU, those rights have to be written out to every object in the OU. The advantage on the Novell side is that it is quicker and requires a much smaller database update. I would suggest you check out the November issue at www.nwconnection.com, it has a good article comparing NDS and AD.
I am a MCNE & MCSE, with more experience on the Novell side so I admit a slight bias...with that in mind, I REALLY want to learn AD because I don't want to lose my MCSE, but it is tough because it just seems so AMAZINGLY complicated compared to NDS, yet still not as powerfull. I still have a lot of study time to put in, but my impression so far is that AD is just NT4 domains on steroids.