I like the table-based metadata editor more, as well. But I also understand (and agree with) the reasons it is the way it is now. It's just a bit unfortunate that the metadata editor is a bit of a catch-22 in its current state. It offers a way to edit metadata in a wysiwyg manner, but using it effectively means that a fairly thorough understanding of metadata specifications and their various hierarchies is sort of a pre-requisite. And having a fairly thorough understanding of metadata specifications and their various hierarchies can mean that manually editing the opf to add metadata might actually be simpler.
But the bottom line for me is that I don't think there's a solution for a wysiwyg metadata editor for epub3 that would appeal to those already knowledgeable and would also be intuitive enough for a novice to navigate.
In other words: the easier it is, the less it can do; and the more it can do, the less useful it becomes to those who understand its use. *shrug*
That's not meant to dismiss the suggestion at all. But then I don't use the new metadata editor any more than (or less) than I did the previous one.