I'm a lazy admin. As such, I look for ways to efficiently spend my time. I like testrail, and have since the first day of the 30 day trial.
The one thing that I would love to be able to do is use variables in test cases. This would be exceptionally useful for writing tests where a tester will need to access a server, but that server name changes based on the environment being tested.
As it stands today, if I need to write a test that will be used for testing in DEV and QA, I have to write 2 versions of the test. Yes, I can copy the test, but that still means managing several versions of the same test.
I could even use preconditions, and list the server names for all the different environments. This shifts the burden to the tester, but humans being what they are, it introduces the possibliity for mistakes.
What I'd really like to be able to do is define variables at the test plan level which would allow the alering of the variables based on the test plan being run.