Microsoft s initial move into the security products market, the ISA Server, has evolved well beyond its firewall roots. Now known as the Threat Management Gateway, the product is being positioned as a comprehensive Web security gateway. The beta release offers enterprise IT shops some solid capabilities, but also has some considerable drawbacks. Microsoft takes a very conservative approach with its security products to minimize customer administrative costs and provide fundamental security that works for the duration of the Microsoft relationship. This long term view has benefits and drawbacks for IT that can be illustrated by TMG.
Source: https://threatpost.com/microsofts-threat-management-gateway-mixed-bag-031809/72404/