Hi - On the plesk 10 domain license, can you have unlimited clients w/unlimited domains - But can only create 10 primary domains? I am planning on hosting on a dedicated server with probably 100-200 individual hosting users on the server

You can only host 10 domains w/ the 10 domain license.

There are other plesk licenses that allow you to host more users. Check with your datacenter or plesk for more info.

nice choice, i personally chose plesk 7 as my control panel beacuse of the professional look and reliability