We have both the Legend RPG
and the $1 Legend PDF available over at RPGNow. Which one do we use more? I can't say we have even opened the softcover book yet.
The PDF? On my tablet and phone, and each chapter is printed out and stabled together in handy booklets. We could even have more than one copy of the character creation chapter printed out so more than one player can reference it when building characters.
You don't know how nice it is to be able to hand someone the skills chapter, someone else the character creation chapter, and keep the combat and adventuring chapters open to pages and ready for use. It's like someone has revolutionized our gaming experience, and I just can't force myself to go back to the hardcover "single user" soft or hardcover book way of doing things again.
And if the character creation chapter ever gets worn out, ripped, and stained I do not care at all, as I can always print out another copy. That isn't so easy with a $50 hardcover. I also have these on a secure and private little place in cloud storage so I can access them anywhere I go. My D&D 5 books? On my shelf, at home. With a PDF, if I have Internet access and optionally a printer I can play.
I like collecting things, and I like collecting books. I like the feel of them, and I like reading them. As I collect more, it gets harder to justify new ones. And for playing with them? I collect, so I always worry about them getting damaged - and many are. But PDFs? PDFs don't get damaged during play. I can collect a lot more PDFs than I can books. And PDFs are way more useful during play. So much so I find it hard to play games that aren't on PDF.
Now there is a limitation to all this. 1,000+ page games need not apply for my PDF good feelings and excitement, as those are way too huge to print out and own in a usable form with just the PDF. I like short, tight, simple games where more of the rules are in a core 64-128 page form, and easily printable and dividable into sections. I feel PDFs for larger games are only good for reference material or online reading, as printing out the spells of even basic Pathfinder would take reams of paper and be a nightmare to use at the table. Even though I have many Pathfinder PDFs, they are not as useful as PDFs of shorter and simpler games.
So there is a sweet spot for PDF games. Short enough to print out everything and organized enough that dividing the book up makes sense and allows players to pass chapters around as needed. The future isn't the traditional coffee-table RPG book collection for our groups, it is taking the form of a smaller, lighter, and easier to use and play with set of electronic documents that can be used how and in the forms we want to use.