I Agree with your observation about passwords inhibiting "Trying". I've bought all the Instrument REs, with the exception of "Radical Piano" and "Radical Keys". I did a "Try" of Radical Piano, with low expectation of purchasing it, because my actual Clavinova piano has exceptional piano sounds built in. I was curious to hear the comparison between them. But in "Try" mode, you have to enter a Password every time you log into Reason, which is too annoying. So I deleted "Radical Piano" sooner than I ordinarly would want to, and I never even Tried Radical Keys. And there are lots of Effects REs I haven't tried either.
Generalizing: When a user has low expectation of actually buying a RE, they won't even Try it, because of the password annoyance.
So for all you RE developers out there.. who wish Users would "just give your Rack Extention a Try, and you'll be pleasantly suprised", we need you to lobby Propellerhead to fix the password annoyance, because its probably hurting your sales.