I have around 15 VPN's for small remote offices (up to 10 users).
These offices have Cisco 877's and 1841's on DSL lines.
They work fine and I regulary scan the internet facing IP's of these routers (using Qualy's Guard) to see if there are any holes.
I've just tested IPS on my home 877 and thought it was quite good. In your experience is it worth turning on IPS for these remote offices or will it impact the performance etc and best leave it as it is.
My home 877's memory is on a constant 77% used since turning on the IPS. CPU remains on 20%.