So what divides well-handled head-hopping and poorly-handled head-hopping? If the PoV is to switch quite suddenly, and perhaps repeatedly, throughout a scene, how can you tell whether it's well-handled? I'd imagine that the new paragraph (the one marking the PoV switch), should open with this new character's thoughts or actions, so the reader knows, but...
How about omnipresent, then? Close narratives seem to be well-favoured, but are there times when an omnipresent narration (as if looking down upon the action) is best? I wondered whether action/combat scenes, for example, would work best this way.
For me, the sure-fire way of spotting a well-handled head-hopper is if, oddly, I’ve NOT noticed it!
I've been so carried away with the story and characters, I've not noticed the head hop until much later! Also, the most successful head-hops establish that this is the norm very early on, so you know what to expect.
The Chathrand Voyage did this a lot by way of an "editor" who was writing the story of the characters. In the opening book the "editor" writes that he's recording the story in the following pages...
It worked well, and readers knew the editor could head-hop because he'd known the events of the story and was merely recording them on paper afterwards. Also, the head-hops weren't so much that they were distracting. One or two a chapter or scene, usually, which flicked back and forth in such a well-handled way, you barely noticed them. And, IIRC, there weren't many (or any) in the opening chapters.
Anyway, then there's the godlike narrator, who usually knows everything everywhere but doesn't always focus on character thoughts (unlike close POVs do regularly). LotR worked well with an omniscient* narrator, IIRC (it’s been years since I read it, though!).
I wouldn't ever write a story that didn't establish head-hopping early on and then drop in head-hops during action scenes. That would look lazy, imo, as if I just couldn't be bothered with the limiting POV of my chosen character and decided to write about everything everywhere that was more interesting. I feel if you write in close POV, you find ways to make it work without losing the epicness of omniscient POVs. Your character could reflect on what others are doing, or imagine it, or find ways of keeping an eye on others. Makes the character more interesting!
* I think you meant "omniscient", not "omnipresent", since there's a slight difference in meaning...