From a consumer perspective, particularly in relation to digital information products, I find that the value of bonuses can be somewhat questionable. Many times I have bought a product and found that the bonuses contain very old or irrelevant material, or are even thinly disguised vehicles to market other products. If however, you are offering a bonus or two that would actually add value to your main product, well then, everyone likes a freebie.
We are as consumers more savvy than ever and if the bonuses are just padding then it will show through, but if you're offering something of quality - which I'm sure that you are

then some well selected extras could just be the icicng on the cake.