Just a quick Accouncement relay from the Patterns and Practices team. Enterprise Library 4.0 March 2008 CTP released.
It's interesting to note that Enterprise Library 4.0 has the Allow Partially-Trusted Caller attribute (APTCA) on all assemblies which prompted some patches and work-arounds to make them work on some environments (eg. usually shared hosting)
Personally I only had the chance to get to know Logging Application Block, Exception Handling Application Block and a little of Data Access Block but I invite everyone to have a look and I'm looking forward to having these integrated with my apps. Enterprise Library is something so powerful that a lot of companies/developers are missing out. IMHO, this is a must for any great developer. If not use it then at least see how it works.