[FleXy]

Note: secondary usergroups was not usefull in latest vbulletin realises, but Additional Usergroups is very-very userfull feature.

The main reason: When you use primary group only, when you create a new one:
* you need to control and correct setting of all forums permisions on your board, becasue by default private forums is allowed to access for new usergroup. if its many forums with not default setting - its a big work you you to control and correct setting when you add new forums or add usergorup.
* hard to correct usergroup setting and compare that new usergroup have no less permissions every time [/B] when you change setting for general usergroup (for ex. registered users changed default avatar size from 50x50 to 100x100) after that you must go and correct other usergroups: Uploaders, VIP, etc. etc. and give them 100x100 also! bad..... unnecessary movements!!!

when you use additational usergroup you can simple dissalow all for new usergroup, avator size set to 0/0 ( settings will be used from primary usergroup) and give only additational permissions only. maybe change attachments size more that primary usergroup have and its will work...
with additational usergroup you can not give less permissions for primary, only additational its fully reflects concept of promotional system and must used to promotions

* Third, you can put "Registered users" not to one usergroup (like primary usergroup change allowed) but you members can be Uploaded, Vip member, Customer etc. at the same time!

sorry for my english, but I think you understand main idea why i use additational usergroups and there needs