OpenNLP is great. I've used it for a lot of subtasks, but nothing that produces end results as described earlier. It's an amazing library for building NLP systems, but doesn't produce anything directly (named entity recognition, etc) Typically it's coupled with other libraries.

The big problem I think with NLP in general is typically to do anything, you need a pipeline. (Sentence segmentation, tokenization, part of speech tagging) usually at a bare minimum. Then from there you can do named entity recognition or other tasks that produce actual usable results.