I agree, Tony_See, I think this is a big step backwards for a lot of reasons of usability and features.
Here's my biggest concern: when I want to reply to a reply (not to the original post), I click on reply and I get a very small dialog box to type into. If I type more than about one sentence, I can't even see the entire message I have typed, and there's no apparent way to scroll back to the beginning of what I have typed. Nor is there a preview where I can view my entire message. I consider this to be unacceptable and it needs to be fixed immediately.