No. you also have to empty trash. The bulk of the files in most cases are in the application, but sometimes its not. Do a spotlight search and that should help to.
I'm in a similar situation, i had a video project (which took up 20 GB out of 35 remaining on an 80 gb drive), and am trying to make more space.
Another thing you can do is compress unneeded files, and put them in a disk image. Just be wise with them.
-yankeefan