If so, any sweet custom effects or instruments you've created?

First I've heard of this program (not that I am up on any current music programs). What can you tell me about it? I'd be interested to know if it can be used as an instrument tone generator for a master midi keyboard.

Oh man, hrm, where to start. Probably the best thing is look at the website
http://www.propellerheads.se/products/reason/

It's like you can get your own virtual rack of synths, effects modules, mixers, etc.