I'm a huge fan of Snort, but I am more than a little dismayed at the lack of acceptance that it has in the community. Now I know that most people who read this blog will think that I have lost my mind, but hear me out.
There is a mindset that I see with IT people that goes something like this:
Manager: "We have a problem. Our enterprise isn't covered by IDS sensors."
IT guy: "I know just what we need. There's a vendor that has an appliance . . ."
Manager: "Get me three bids."
I call this the IT Appliance Fixation. In my experience, the "typical" IT response to a problem is to buy a box that someone can hang on to the network. The purchase is based largely on vendor advertising, sales pitches and the vendor's website. The problem is, when it comes to intrusion detection, there is no better sensor than a good old snort box. I will grant you that building a snort sensor takes time and writing/configuring snort rules takes time too, but what's the cost benefit ratio?
Assume that a Vendor supplied IDS will cost $50,000 just to purchase. Factor in the time spent finding the right product. Now consider that an organization could easily spend that time configuring a Snort sensor baseline image, and roll that out on computers that are past the end of their life cycle - see where I'm going? Now factor in the open source nature of Snort's rule sets, and you could easily save money in implementation, and use the money to hire a decently paid IDS analyst.
The bottom line here is that the best solution is not always the newest one, or one that comes with vendor support. If you are in a position to do something useful on a network, it does not always have to cost money.