Very. That (several sensors), and honeypots. You need to have
tiered security posture... an IDS is not an 'end-all-be all'
sort of thing -- it's just another tool.
Personal experience and opinion, of course. 
$.02,
- ferg
ps. I don't believe in 'self-defending' IPS autocracy stuff;
you usually end up sepnding more time clearing auto traps as you
do setting them up.
Fergie wrote:
Hi Ferg,
All-in-all, I find that an IDS (NFR-style) has a quite useful
utility.
How is it useful for your network?