buildstats now provides a whole bunch of information on performance, as explained in bug 8842. Richard Purdie would like some of that information displayed in Toaster, and also the ability to see which tasks were running simultaneously in parallel. This was his request: 

"you really need several of the numbers to understand exactly what may have been going on within the task and there isn't one number you can show which tells you everything.

This is a bit of an aside, but another "missing" piece of information
is "what was going on in the system at the same time as this task?".
This is the kind of information that the bootchart graph shows really
well. If we could click on something and see which other tasks were
running at the time this task was, that would be information we can't
currently easily obtain.

That data is there, we know the start and end times of each of the
tasks, so something can compute which ones were running at time X, but
its not something that anything is currently doing as we don't have an
easy way to display that on the commandline."

Yocto Project maintainers seem to be the users most interested in the performance data. They seem to believe it can help us diagnose the cause of errors, and better track system performance. It does make sense to cater for their and the QA team use cases.