I have not had any experience with demagnetising discs, but as WM mentioned, I have had some nice success using antistatic sprays. I use RA Relees and it makes quite a noticeable improvement in my system. So much so that I routinely treat every disc with antistatic.

I find I generally get a more analogue feel, less hardness, smoother more detailed treble and slightly more controlled bass. For £20 it is not too excessive a price and the stuff I have has lasted years and hundreds of discs.

Henry is right, photocopier antistatic liquid works just as well. The xerox antistatic liquid I have at home does the same job.

Cheers, Robbo