Up until yesterday, it was all paper, simply because I did not have an eReader or tablet. But I bought a Nexus 7 on the weekend and I'm now in the middle of reading Typhon Pact: The Struggle Within. And I will be looking at the other ebook-only releases (Slings and Arrows, etc) at some point.
Going forward through, I think I will be sticking to paper books when I have the choice. Maybe. I haven't really decided yet.