I don’t know when they released it, but it has a huge amount of fixes and improvements.
The Release notes page says it all.
Apparently they did it yesterday.
Today, we’re excited to announce the release of ReSharper 4.1! This minor version is highlighted by:
Support for Microsoft Visual Studio 2008 SP1
Enhanced ASP.NET experience
Improved performance and usability: quicker solution load, optimized Unit Test Explorer behavior, and more
New minor features, including name editing in code generation UI, generating backing fields for implemented interface properties, highlighting usages of XML tags and attributes
Stability improvements and bug fixes
See Release Notes for details on bug fixes, cosmetics, new features, resolved performance and usability problems.