absolutely. i like pdfs but find them very difficult to incorporate into the game. elements of magic is the only one so far that i've used in the game, and god-willing there will be a print version soon because my inkjet printout is four weeks old and about dead.
speaking for myself, i think it would be great if i could look at a free pdf online and then go out. i would like to spend hours at my FLGS browsing books, but usually i go out of a specific need for my game and there are alot of books that could be right, but i'm unlikely to spend more than $15 without having looked through it. so there are a lot of books i never really consider because i just don't get to the gaming store that much.
as a buyer profile, i've got a 3e/d20 collection weighing in at around thirty books, over half of which are hardcovers costing $25-40, plus probably ten pdfs i've purchased. other than elements of magic, the pdfs haven't gotten any playtime, and the hardbacks get more playtime than the soft.