We are using roaming profile today and size is 10-50 MB on current terminalserver environment per user. We have redirection of favorites, desktop, my doc/music/pic/vid so this is not stored in profile.
From day 1 we will only have 50 users. But in 3-4 months after that 1.000.
Login time today is 22 seconds for a 22 MB profile and all the GPP settings.
Don't know Profile unity but will check it out.
JV