Well, I can only comment from a buyer's view on this interesting topic.
I just had a look, how many PDF's I've bought so far from RPGnow, and that's 17 up to now.
Where did I hear of those products? That's almost exclusively EN World. I'm not browsing the online store on a regular basis, but only go there, when I read an anouncement, or even better, a review on this site.
Which products do I buy as pdf instead of print? Well, that's tricky. These are more or less three kinds of products:
1) Products I don't expect to see in print, never ever that is

.
2) Products, where the topic doesn't interest me that much that I ever wanted to buy a print copy thereof.
3) Older products, where the print copies were more expensive than I ever wanted to pay for that topic.
Would I buy more pdf's under other circumstances? Well, actually yes. But I have to admit that this is a vision for the far future. I would like to see the devolopment of a new kind of print industry, something like "Print your PDF"-service stations. Then I can buy my pdf's, and if I really like them, I'll go there and let them be printed. Nowadays there is always a risk: Do I like it *that* much that I will spend even more money on the product by buying an additional print copy afterwards?
Do I register anywhere in order to get hold of a free copy of some "cool" pdf? Actually no. Who says it's really cool? I won't sit there and fill out boring forms in order to get my hold on something I actually don't know anything about.
Why are there much more downloads of free products than of products you have to pay for? Well, I've got DSL and a flatrate. That's one click. Any more questions

? I suspect that only 5% of those downloads get actually read. The rest waits for the next harddisk crash.
When on the RPGnow website, do you look at other products? Yes, I do. Most of the time, I browse the two columns on the right, best sellers and new products. Anything else? No. Except sometimes a link to "other products of this publisher", if I like the products, that is

.
But there's this handy list of all fantasy products with pics and descriptions shown with a link in one of the prior posts. Yes? Oh, really! Looks great! Where did you hide this one

?
Do you look at the customer reviews on RPGnow? Well, yes, I do. I don't trust those 5 star reviews (unfortunately most reviews are 5 star, which invalidates them a bit in my eyes). I usually begin with the worst review and ask myself, whether those points the reviewer made may disturb me. Most negative reviews give a good insight into a product, but I take them as personal view, so they might actually convince me to buy a product

. Usually I don't consider buying a product without a single review. Therefore, reviews help, definitely.
There was something else, but I'm afraid, I forgot it for now

. Okay, next time

.