I'm using both. I haven't happened to read a book on the built in flash since the firmware update, so the problem there may have been fixed. I don't mind the slowness in booting too much, I just pour myself a drink or something while it does that. I don't use public transportation much these days, so generally I read in the comfort of my own home.

It's a pity about the battery life, although it might stay on long enough to read the book. I hope bookeen fixes these problems soon.