WordPress MU

I have a content submission blog running on wordpress 2.7. The reason I didn't use wpmu from the first is there're plugins yet not compatible with wpmu 2.7

I'd also like to have a community, so I'm thinking to use buddypress.

What I'm dreaming here, is my buddypress users can also login to another wordpress installation, hopefully with cookie support, so users kept logged in among different wordpress installations.

The buddypress site will be on example.com (parent)
and other sites are (children) site1.example.net, site2.example.net

Whoever logged in to example.com can use children sites, using wp_users from the parent.

I really don't mind paying this, but either I post this on some coder site or not, I thought I should know the proper method in order to outsource effectively.

So, do you think is this possible?

"The reason I didn't use wpmu from the first is there're plugins yet not compatible with wpmu 2.7"

Do you know which ones they are? It might be better to get the plugins that you need to work with MU, than to try and do the setup you're describing.

Last time I used, before version 2.7, maintenance mode caused site to work so slow. Also since mu doesn't support easy update of plugins, it's easier to use seperate installs.

Also since mu doesn't support easy update of plugins

In fact, it does :)

maintenance mode caused site to work so slow

What maintenance mode?

maintenance mode, the plugin.