Just a quick note in case you missed Grigori's announcement on the patterns & practices team's plan to focus on Dependency Injection in the upcoming release of Enterprise Library, now apparently known as v4 (not v3.5 as announced previously). If you have any wish lists please provide them directly to Grigori or on the CodePlex site.
My personal vote is to integrate this deeply with the Policy Injection Application Block, allowing for dependency and policy injection in one fell swoop, for example:
IMyService = PolicyAndDependencyInjection.GetMeAFullyConstructedAndPolicyEnabledInstanceOf<IMyService>();
Time will tell if that's what we'll get. But I'm paying a visit to Grigori and the team in Redmond next week, so hopefully I'll get a better picture of what they are planning very soon!