rules engine in wwf or biztalk…..

basically I'm looking to integrate an application with a rules engine, so that users can tweak their business rules without having to tweak the software…..

 ideally the engine should be….

 i) fast…it need to do real time processing of automated processes….say < 1 second to evaluate 100 rules….(I know this is a bit of a 'how long is a piece of string?' sort of meaningless thing….but it should be lets say > 10% speed of hard coded rules in an app.

ii) easy to interact with…I've messed about with the biztalk rules engine, I'm somewhere in the novice category, there doesn't seem to be much documentation on structuring rules, though the rules initially seem intuative, the engine is in fact far more subtle (and powerful) than it first appears……I am mildly concerned non developer users will get themselves in a mess.

iii) able to handle >10, <1000 rules in a relatively structured manner…….it seems initially easy to develop spaghetti rules……I wonder whether I can chain policies together to isolate different areas of the 'app'

 Any links to idiots guides to designing rules in either environment is appreciated.