yes it is indeed worth it!
to whet your appetite though, GNU is an operating system conceived way back when by richard stallman, because he was pissed off at unix being proprietary. he called it 'gnu's not unix' to help avoid any legal hassles because he was trying to make an OS that did exactly the same things as unix, but which had totally different (or original at least) underlying code, code which would then be free to be released for anybody to see and modify. this was his way of saying that you didn't need to dance to at&t's tune (or anybody's) to get a decent operating system.
sadly gnu ran into a lot of problems coming up with a working kernel (which they still have not resolved 20 years later) but luckily they were eclipsed, overtaken and partially absorbed by other endeavours in the meantime, and GNU helped create the varied and full operating systems we have today. in linux for instance, even though the basic system is linux, many of the utilities and quite a few of the programs are from the GNU system, and are still maintained by the free software foundation for the good of all users of the software.
[ January 09, 2003: Message edited by: Calum ]