Although I own a BeBook, I think out of the currently available readers I'd recommend a Sony to any friends/family thinking about buying one. I just don't like the idea of vendor lock-in which you get with the Kindle especially now Sony has added EPub support. It seems the Sony readers are now about as open as any general reader would need.
As for me, I prefer the BeBook with OpenInkpot.
I bet the kindle sells really well though, Amazon have such a customer base that just a few ads on their site will draw people in.