function-points

Some questions about Function Points: 1) Is it a reasonably precise way to do estimates? (I'm not unreasonable here, but just want to know compared to other estimation methods) 2) And is the effort required worth the benefit you get out of it? 3) Which type of Function Points do you use? 4) Do you use any tools for doing this? Edit : I am interested in hearing from people who use them or have used them. I've read up on estimation practices, including pros/cons of various techniques, but I'm interested in the value in practice . Mike Cohn in his Agile Estimating and Planning consider FPs to be