Between Selenium IDE and WebDriver, Selenium IDE is a Record and Playback tool but is not reliable. Since web applications are frequently changed, the IDE is not a good solution for a production environment.
Assume that you recorded your test, and you found an element with a dynamic ID. Yes, you can import it into eclipse, but what happens when that test starts failing? But why not simply make your test agile and independent to catch these in the first place?
So, IDE is designed to be a quick solution to automation, but it is not a solution to a full regression suite.