Oh yeah... there's a poll here.
I spent my original $50 at the Sony store. I haven't bought anything else from them. I can't. They don't support my computer and OS (Mac OS X).
Too bad for Sony! I spent about $400 on eBooks and eMagazines in the past year. None of it with Sony. Their store won't let me in the door -- it's like they don't want my business.
I have easy access to a Windows box (that isn't work's) about twice a year when I visit my sister's family on vacation. I have no intention of purchasing a copy of Windows (even to run on an Intel Mac), so I really wind up feeling like Sony doesn't want my business.
Instead, I've done most of my eBook purchasing at Baen, with a little bit through Fictionwise. And a bunch of PG texts too, of course.