Snort takes a full-time TCP/IP and security expert to baby-sit it and sift through false positives. Fun CS project, but not realistic for a business.
Meanwhile, lots and lots of people make NIDS. I think the biggest players are cisco, palo alto, fireeye, and juniper. All of them have significant cost associated and do not require a bunch of 3rd party junk to work. 3 out of 4 of them also have integrated appliances - firewall + IDS/IPS, VPN, etc which can be handy. They also all have their various pros/cons. I recommend trying them out if at all possible.
One's mind, once stretched by a new idea, never regains its original dimensions.
--Oliver Wendell Holmes
Crunching for Team AnandTech!