What frustrates me about the UI is that I have exactly 0.71480550 BTC, and when I type in that I want to sell 0.71480550 BTC, it says I don't ahve enough funds to proceed.
THAT is why the new UI sucks. Oh, and also how you can't copy/paste values any more. That makes everything so slow.
Also, copy paste does work and you should make sure you don't have any opened or pending orders.