I have been using it for a while and it is pretty good to find long tail keywords. For example... start your search with "how do i" or "how can i".. you can also expand the results by clicking on them. Tool: http://ubersuggest.org/ It's not mine, just sharing
Pillai is right, I been using long tail pro for a few months now. Its best tool I ever used. Very easy to use.
Yet another vote for Long Tail Pro. It is a very solid piece of software. I have been using it for a while now, and it is quick and easy to use.