Offering Review Copies, cool?

Agreed. Transparency is important.

The rule actually applies to offering bonuses in exchange for reviews AFTER the purchase. That is against the rules because people who have not yet purchased the product have no way of knowing those reviews were incentivized. It's also a LOT more likely someone will write a favorable review when a bonus or discount is dependent on that review (ie the bonus is delivered only after the review has been left).

When review copies are offered in the actual sales thread (yes, I use this technique) buyers are well aware of this and will know that when reading the reviews for the product. Having said that, by offering the discount BEFORE a customer buys it means that customer has nothing to lose by leaving a negative review and nothing further to gain by leaving a positive review. All the technique encourages is the act of leaving a review but since the discount has already been given before the review is left, it is much less likely to sway that review.

I also point out to all my customers that I only ever want their honest feedback. I agree with others above who have said a WSO thread littered with realistic comments, some negative and some suggesting improvements, is much more likely to resonate with potential customers than one that is only full of glowing testimonials. So I encourage honest feedback from my members because that is exactly what I want. If they think there is an improvement to be made then I want to know about that... and all product owners should.

The reason I began offering discounted review copies was because I got sick and tired of reading all these glowing testimonials from people who had been given a free copy of the product. It's very easy to say something is great when you have not had to invest any real money in it. I figured giving a small discount was a much better way of doing things and would result in a lot more realistic reviews as these people have had to invest their own money in the product.