4.3 VS Extension vs 4.5 Bolt
Support for all versions of Visual Studio 2008, 2010, 2012, and 2013 except Express.
Desktop-style Explorer, Statistics, and Source views have been replaced with Bolt Code Coverage window.
Code coverage is available for most recent test run only.
Trend and historical data only available in Desktop.
Run and debug MSTest and NUnit tests with fully integrated code coverage.
Branch coverage visualization in the Visual Studio editor.
Developer-centric code coverage view in Visual Studio.
Setup/teardown test timings for each coverage run.
Test run prioritization.
Command line test runner.
Portable test result export (JSON/XML).