I believe that knowing the basics of how HTTP works and the meaning of HTTP error messages is prerequisite to performance testing and analysis with any tool.
You can depend on more expensive tools to mask the complexity for you, but a fool with a tool is still a fool. Harsh words I know, but if you don't understand what you are performance testing, you won't recognize when tests have gone wrong and will be setting expectations based on invalid results.
With that said, if someone reviews the test data and determines that the results are valid, then I think knowledge of HTTP is of no significant value in further analyzing the majority of test data generated by OpenSTA. My point here is if someone confirms the validity of the data, other folks who lack HTTP knowledge can interpret the data and make productive use of it for capacity planning or regression analysis.
For example, all the collector data (from Windows Performance monitor and SNMP) can be interpreted without knowing HTTP. Understanding the relationship between response time data, workload, and system utilization is independent of knowledge of HTTP internals and can be gleaned from data presented by OpenSTA.
In my opinion, this really depends on how your scripts were created.
For example a request for a page may consist of 10 http requests and responses (page + images/css etc.).
If you didn't know how HTTP works you might just look at the request for the ASP page (for example) and decide that is your page response time; or you might sum all the response times of all requests together and decide that is your page response time. Both of which would be incorrect.
Now, if the person creating your scripts knows HTTP then they could use timers to record the response time. So, if you looked at the Timer report you could see a more realistic response time.
So it is possible for someone who knows HTTP to create scripts in such a way that you don't need to know HTTP to read the results.
However, I think you'd struggle to really *analyse* the results and investigate any problems that may arise.
Everywhere's within walking distance if you have enough time.