Here is a new maintenance update: TeamCity 4.0.2.
In this release we addressed some bugs and several performance and stability issues.
Improvements include better "merging" of automatically triggered builds in the build queue, ability to checkout on agent with TFS version control and IDE integration fixes.
You can view the list of the resolved issues in our tracker.
In the mean time we are working on TeamCity 4.1 which will include new features and many improvements.
The EAP will open soon, so stay tuned!
See also related TeamCity Dev blog post
--JetBrains TeamCity Team