Bear is a relatively new application. It seems to be very popular.
I have fooled around with the desktop application, but I have no real need for the iPhone and iPad apps at this time. This might be the reason why I find it less than compelling.
It has a clean interface, and I like it. Whether it is "beautiful," as they claim, I do not know. To me, it looks like many other note-taking apps on the Mac.
They claim: "Link notes to each other to build a body of work. Use hashtags to organize for the way you think. All notes are stored in portable plain text. Yes, it allows you to link notes--very much the way that nvAlt allows you to do it: You enclose words in double brackets, and if those words correspond to a note title, it links to the note. This looks like a wiki-link, but it has only some of the characteristics of a wiki-link. Chhange the title of the note and the link is broken. No back links either.
Bear supports its own version of Markdown and has a "Markdown compatibility" mode. It handles pictures very well, and it also exports to PDF and Word, and it has many other interesting and useful functions. It is a good applications. I recommend it, but I myself would have liked a stronger linking capability.
I would very much like to see something like "ConnectedText for Windows," and I had some hopes "Bear" might be it. But it isn't. To be sure, this is a very esoteric expectation, but I cannot help myself.
If you would like to see a more thorough review of Bear, see here.