A user interface is well-designed when the program behaves exactly how the user thought it would.
Good software, like wine, takes time.
Something is usable if it behaves exactly as expected.
If something seems possible, that's probably because someone is already doing it. When something seems that it can't possibly work, nobody tries it. Real innovation happens when someone tries anyway, overlooking an obvious flaw, and finds a way to make an idea work.
Nothing works better than just improving your product.
Never put yourself in a position that will put yourself at risk if you make the wrong decision. We spent cash on everything. It's fashionable to make 'bet the company' decisions, but don't do it.