Lucene is truly an amazing piece of work. A knowledgeable Java programmer can pick up the API and integrate lucene into their applications very quickly and effectively. There are some excellent examples that come with system, and getting an index built and a search system working is a fun task you can complete in a short afternoon.
There are, however, some conceptual hurdles. Lucene aims to be, and is, an excellent search engine, and nothing more. Surrounding Lucene are a number of other projects and tools for parsing documents, extracting blurbs, highlight results, and so on. On the flip side, Lucene it's self is amazingly configurable. Out of the box is has some excellent defaults, but you can change every aspect of the system.
The "Lucene in Action" book can provide you with the big picture. The book provides excellent examples and give you pointers that will save you time, and make you look (and feel) like you have been developing search systems your whole life. I have the Lucene in Action book now, and I'm using it to re-factor my software application. Had I owned the book at the beginning of my project, I would be six months ahead of where I am today.