We have a Terrastation Pro and have had no end of trouble with it!!
The main problem is you have to downgrade your firmware to 1.0 for it to work in AD (Advice from support).
Also it is not fully AD compliant as you can only add about 600 users from the AD, this is a big problem when your school has over a 1000 like ours.
You are also limited to the Terrastations form of security and you cannot right click and set windows security settings for folderand files.
Overall we are disappointed with the features of the Terrastation and actually asked for our money back but had the misfortune to phone their VERY rude unhelpful support line. :x
We only use it for backups now.
Mike