At least the first one, Scalzi's "Old Man's War," I've already read and blogged about. But I haven't started on Robert Charles Wilson's "Spin" yet before they sent me something else.
I'm not enough on the producer side of the writing market to have a strong opinion on the advantages & disadvantages of giving away content. I'm still mostly a consumer, and therefore my attitude is more along the lines of "cool, free stuff." What I haven't worked out yet is the practical mechanics of reading a whole electronic manuscript. I can't bring myself to sacrifice that many printer pages, reading them on the computer on the train seems lame, and I'm too cheap to buy an e-book reader. Well, maybe Heather can show me how to put it on my Ipod, I've seen her do it. But being the new-media download junkie that she is, I think she's already moved on to a Kindle.
Anyway, you want free electronic books, check out Tor's website. Why not?