Since our environment includes JIRA I'm looking forward to this upcoming feature as well. This may already be planned, but I would suggest some dashboard gadgets as part of this plugin. I've written a couple of stand-alone gadgets for some implementations I've used, and perhaps something similar has been thought of.
I have one that will display the results for all of the active test plans and test runs in a project. It combines some of the data displayed on the Test Runs & Results page in the Detail and Compact views.
In my implementation the value of the project is hardcoded, but it would be nice to have an Edit link and be able to choose that from a list of TestRail projects.
The other gadget displays the testing status for a particular test plan or run.
Again, my implementation uses hardcoded values, but choosing the project, and the specific test plan or test run would be good options. This type of gadget would probably be good for showing all of the results for a particular milestone as well.
Overall, both gadgets used hardcoded values for the TestRail URL and the credentials for the API calls, so those would probably be good options at the Administrator level for the plugin.
Again, these were just suggestions for possible gadgets to be included in the plugin.