Having worked on a number of med-large web projects I can recommend the caching block from ent library as it allows you to use nCache or similar with a simple config change. This allows the dev team to use TDD without the need for nCache (or similar) to be installed everywhere.
Log4Net is far superior to the ent lib logging block IMHO.
Security / Crytography blocks I have used a few times and generally find that they do what they say on the tin without being too onerous or complicated.
The rest of the framework is beaten hands down by other simpler and (IMHO) better solutions
Data access - nHibernate, ActiveRecord, Tarantino
Unity - windsor, spring etc
Validation - I use the castle stack
