This is a must have for Drum & Bass producers... especially for neurofunk... the fact that it's free is insane! Sounds great on basses with a huge helping of distortion! The only thing I would add be an option for it to automatically disable the filter when it reaches 0 for highpass or 100 for lowpass for some drum filter sweeps. You can accomplish the same thing by automating the bypass setting in your daw.
I did encounter a bug when I deleted the plugin from a chain in Reason 10 and it crashed the plugin instead of deleting it. The other plugin instance kept working though.