I have one, and whilst it sounds nice, I never had a break in my hopper before I fitted it. I kinda regret it now, but I have removed the magnetic clutch and just use the standard drive in it, but with the new drive cone.
The magnets are fiddly, the manual gives you abot 50 different ways to configure it with no real explanation of what the difference is, as it all depends on the pattern that you put the magnets in.
If I was you, either find someone with one who saw an improvement, or save the £30.