ROI on IDS/IPS products

I was talking to a junior security administartor working for a big
telecom company.  He said something which is worrying.  After few
years of IPS deployment in particular department, they  decided to
remove IPS devices.  It was felt that they did not find enough ROI to
justify 2 dedicated personnel to monitor and analyze IDS/IPS logs and
reports. It apperas that no major incidents were detected by network
IPS devices.  they felt that signature coverage is either poor or not
timely. i also was told that these IPS devices are from industry
leaders.

Can you share your experiences?  Any examples of successful detection
and prevention of major attacks and penetration by IPS devices.

Thanks
Ravi