WordPress MU

Hello,
I want to use wordpress mu in an university enviroment. I want that all my estudents own a personal blog. For me will be very important that the student can make search between the others students post throught keywords search using tag Ultimate warior or Keywords Jerome plugin.
Can I do that with WP mu? how?
Thanks

I am interested too, also I would be interested in tagging pages, I remember having seen a post somewhere about this but I can't find it anymore.

as far as I remenber on the homepage of UTW there is a kind of ajax search example for tags but I never tried it...

http://mu.wordpress.org/forums/topic.php?id=2397

Thanks I will try.
This hack is for searh across categories, isn't it?

It's for sitewide tags, which is essentially the same thing (global categories).