How does the IDEA Community Edition compare with Eclipse?
The best, straight answer to this, is to look at the feature matrix of which features are still left in Ultimate-Edition. Eclipse probably has support for all of these things, although the quality of the integrations can always be an issue.
IDEA is a far better IDE than Eclipse (general opinion by people that use IDEA).
On a feature point of view, everything that IDEA CE can also been done by Eclipse. However, IDEA is a commercial product, which limits its adoption. Thanks to the Community Edition, you can test this IDE for free, in order to develop JavaSE applications (or Scala or Groovy). For an enterprise, this is quite limited, as you will not be able to develop J2EE applications.
My conclusion is that IDEA CE is only a tool that allows you to test and understand the philosophy of this IDE. If you are convinced by IDEA, then you will really have to choose between the Ultimate Edition, which will let develop any kind of applications, or stay with Eclipse.