1. Importing Datasets From Excel, SQL Server and delimited text files. In previous versions, data sets could be imported only from CSV files. The current version additionally supports Dataset import from Excel files, text files with a custom field delimiter, as well as any SQL Server select statement. 
2. Suppressing errors and warnings. Now you can have StresStimulus ignore errors and warnings that you do not care to be informed about. Such errors will be excluded from all reports and graphs. You can also cancel suppressing errors and warnings.
3. More ways of finding hidden errors. Now you can compare a recorded test case with an iteration not only in the waterfall diagrams but also from the activity diagram.
4. Agent listening port is configurable now. In the previous versions, the agent listening port was 49998. Now you can configure it for every agent.
5. Test log query enhancements. The test log querying tool in the previous versions was more limited. For example, you could not select responses without errors. Now you can query responses with Successes, Errors and/or Timeouts or any combination thereof.
6. Extractor tree multilevel expand/collapse. In the previous versions, Expand / Collapse buttons on the toolbar either fully expanded or fully collapsed the Extractor tree. In this version, every additional click on the Expand button displays one more hierarchical level. To display the entire tree, click the Expand button several times. The collapse button works the same way, but in reverse. This improvement enables you to display as many or as little details on the tree as you need.
7. Extractor tree is fully hierarchical now. In the previous version this tree was flat. In this version, an extractor from an extractor is displayed hierarchically on the extractor tree.
To navigate to other parts of the v4.3 release notes, click the links below:
4.5 is available here