Rate the Intrusion Detection Systems?

Swannie asks: "The company I'm working for is looking into Intrusion Detection Systems. I was curious on how good/bad/ugly/cute/cuddly LIDS (Linux Intrusion Detection System) is when compared to other, commercial, systems like Cisco's NetRanger, etc. I'd be interested in information from my fellow geeks that have deployed LIDS in real world situations, as well as anyone that has switched to LIDS from a commercial solution, or vice-versa. Hopefully if I have some ammunition to go to the powers that be, I'll be able to utilize an open-source (and less expensive) Linux solution instead of a more expensive commercial one." Are there any other options out there which can be added to this comparison? In an odd bit of synchronicity, this article popped up before press time, which offers up another possible answer, in the form of Snort.