When to use Selenium IDE?

Hi, I am a PhD student currently working on Selenium IDE extensions. I am especially interested in improving the testing experience trying to extend the Selenium IDE by adding advanced features without complicating the recording process.
I would like to gather some expert experience about when it is recommended to use Selenium IDE and when it would be better to manually code the tests using the Selenium API. I also would like to know the average size of a test suite (number of tests, number of commands for a test), does this size affect the decision of choosing the test generation method?

If someone has some experience working with Selenium and is interested in helping me to better know real testing situations, please let me know.

Thanks in advance! :-)