If you're a design control freak then
Social Engine is the shizzle, there are many great off the shelf templates that can make it look remarkably different. The user interface is completely customizable just like using wordpress widgets. Menus are all customizable and there are so many cool plugins you won't have any trouble adapting it to suit your site. Better still it's all open source, meaning that while you need to pay a license per site, you get access to all the source.