Open Source Security Information Management (OSSIM)

Does anyone have any experience using OSSIM?

I'm looking to beef up security at a school having about a thousand  
computers, about 800 of them laptops that students and staff take home  
and bring back, and a bit over a dozen servers (many of which are  
planned to be taken out of service).  In addition, they have an open  
wireless connection (though connectivity to the internet is restricted  
via ISA).  The school is rapidly growing, and while they've been lucky  
to have mostly benign students, I think the security is inadequate.   
(I'm looking at some other stuff too, like some firewalls to  
compartmentalize the network.)

I'm looking to OSSIM to try to help bring a much greater insight into  
what's travelling across the network.  In particular, I like the sound  
of anomaly detection, a consolidated place to view all events on the  
network that can be filtered as needed (to isolate the behavior of a  
particular box, and thus a user).  Of course, these are imperfect  
sciences, so I would love to hear how it fares for others.

Ideally, I would like to set up just one OSSIM box to have it monitor  
the network, but it looks like it would really need agents,  
particularly on the servers.

Naturaly, any other opinions, feedback, or advice would be great (even  
if its not about OSSIM, as long as it helps me get to my goal).

Thanks.
--
Neil.