I'm at university studying Music Technology, I'm familiar with industry standard audio editing software and have been for over 5 years now and I STILL use Audacity from time to time. It's brilliant in its simplicity, and being free makes it even more appealing.
Some of the processing you can apply is surprisingly high end for a free piece of software. I will often import tracks into Audacity just to use some of the tools, such as the noise removal, before going back to the higher end software.
Definitely worth a look, really powerful little piece of software!