The US court just stood by its decision to NOT allow an injunction again Samsung Galaxy products in the US. I wouldn't make that ongoing ugliness a factor in your decision.
I like many things about the Iconia A100, but it's screen has more glare and poorer viewing angles than the HTC Flyer and Samsung 7 Plus. I didn't find that hard to live with except when reading books, so if your focus is books, the A100 wouldn't be my first choice.
Given the $200 price drop on the Flyer, I don't foresee a significant further price drop. The Samsung is a little expensive given the current trend towards inexpensive tablets, but so far that hasn't motivated Samsung to do serious price drops on the Galaxy Tab line. But perhaps we'll see some retailers running specials? Who knows.
HTC has promised an upgrade to Honeycomb ever since the tablet first went on sale. Err... 5 months ago. What could possibly be going on there is anyone's guess. I personally own a Flyer and do use it as my eBook reader. For reading, it doesn't matter much whether it's running Gingerbread or Honeycomb. But I'd love to see the pervasive pen support that's obviously possible in Honeycomb given what HTC did with the 10" Jetstream.