I kind of went through the same exercise, but 2 things made me go with the iLiad Book Edition:
1. The screen/device size was the optimum, IMO, for book-reading - 6" felt too small, 10" seemed like it would be too big. Why only one 8" is on the market and none in the pipeline, bewilders me.
2. The Astak products were supposed to be on the market this past November - even their site still said that. But when I called, it was Spring or Summer. But based on past estimates, I figured I might be in for a long wait.
So I went ahead and got the iLiad
Not saying it's the best for everyone, but I like it.