My own experience parallels tmoody's. I generally read on a PDA with a 3.5" screen or my smartphone with a 2.8" screen. I find I narrow the reader window on my PCs to be similar to the 3.5" screen.
One minor advantage: I fell off my bike and broke my shoulder, so I'm reading one handed. Hardcover, awkward; paperback, hand-tiring; light, small, PDA ... priceless.
Regards,
Jack Tingle