I like it. Plenty of features I'd like to have, but none of them are so obtrusive as to get in the way when I don't need them. The theme kinda reminds me of Atom, but I'm guessing the colors are just popular now. Not that I mind at all.

I have noticed a couple of issues. Namely: the filter portion doesn't seem to work as expected. I typed "object" (without the quotes) into the search bar and it filtered out the entire file. It seems as though it doesn't look through keys.

It would also be really nice if the tree/table side interacted a bit more with the editor side. For example:

1. Highlighting one side the the other side was highlighted.

2. Highlighting filtered sections

3. Maintaining what branched were folded/unfolded between updates

I also just discovered that the slider to the left of the filter field actually unfolds and folds the tree to certain levels. I really like the feature, but that could be a bit more explicit.

This isn't to put down what you've done at all. I really like what you have here (and definitely getting bookmarked) but the question of whether the product wants to be a JSON viewer/explorer or a JSON editor doesn't seem to be answered. It can totally be both, but I'd focus on one or the other first and add to it as opposed to 3/4 of each.

All in all, very intuitive and usable, with plenty of potential to go even further.