I have just gotten around to reading this thread, although I have meant to for a while.
I am in a different camp from some, I actively read using two different devices, an enTourage eDGe and a Sony PRS-300. The eDGe fits a niche that I have long wanted filled, it is great for tech books, reference material, notes, etc. The PRS is great for casual reading like novels, etc while I ride the exercise bike, watch TV, etc.
I have been pulling ebooks for a some time as I waited to get my reader (eDGe was first, Sony just recently), so my TBR pile is pretty big. Having seen some of your posts, your first three books from this series are on the pile.
I will probably only ever buy a paper book again if it is a reference book, programming book, etc, and then will expect to get a digitial edition with it (like o'reilly does). For novels, etc I will not be buying paper again. From my co-workers who have gotten e-readers, only one has started reading paper again, and the only reason he is doing it is he is borrowing from family members. So I doubt that free ebooks will impact your paper sales, I just don't see many people go back to paper after getting into ebooks.
I will probably not ever buy an e-book without a sample available (ala Smashwords), unless I really know the author (previous works act as samples).
Now, you know you can't get me as a paper customer, how do you get my money from me. Say I read your first book and love it. I want to read more (for you, right now I can, since your next two are free also, but say I have read those too, and clammoring for more). I want to read your 4th book, All I see it available in is DRM encumbered sites (SONY, Barnes&Noble, Kindle, Kobo), many who want you on their reader or none. Being who I am though, since this is the only option for your ebooks, I will probably never get the first three books off of my TBR pile (the pdf is tempting, but a poor format for e-reading). Because, is it worth my time (no other cost so far), to read three books of a series to be frustrated not being able to read the fourth?
Now, say I'm tempted by your writing, and decide to muddle through the fourth book in PDF, so I do read this series and enjoy it. Say I decide to donate directly to you, and when I go to your website, the donation link is paypal. Nope, not going to happen. No matter how much I enjoy your work as an author, I will not use paypal.
This is another point I think Authors need to be fighting with their publishers. If I read your book and enjoyed it, I would be likely to buy the new one, and probably by the back catalog, however, more and more, I see being locked out unless I am willing to cave to the blessed device, service, etc.
I just finished a book I got off of smashwords for free (Haven). Eagerly awaiting more from this author, and will have no problem spending a reasonable amount to get future books. I have also recommended this to many others I know that read and would enjoy it. There were a few issues with the book, but not many (no more than I have seen in a lot of paperbacks), but the story was good, would like to see more from that world.
I also just got some games for my system. It was a bundle, pay what you want type thing, you could weight your donation to any of the games, or allow it to be split equally to all parties (developers and 2 charities), so I could have paid $0, or $100, and could have given $100 and all to the EFF, developers get none. I gave a decent amount (what I felt it was worth), and others did too. Each of the developers and the charities got something around $125,000+ in the 7 days I think (more than $1million US to the 7 orgs). No DRM, not encumbered in other ways, and every person could have given nothing and gotten the games (btw they showed up on pirated sites, even though you could get them for free officially).
http://www.wolfire.com/humble This shows people are willing to pay for what they see has value.
Anyway, back to your question:
I don't buy paperbacks anymore, so I am not able to support you that way.
I will not use paypal, so I am unable to donate to you directly.
I will not buy DRM encumbered books, so I can't buy your ebooks either new or back catalog.
So, although I am probably close to your perfect target audience (I have always read sci-fi), I have been locked out of supporting you as an author. As it is, your first three books will probably stay on my TBR pile until I can see an easy way for #4 to moved on, since it is frustrating to read 3 books and know the 4th is there, but not for you.
Hope this helps, anyway, that is my opinion.
--Carl