I was a Vim user for 4 years now but org-mode caused me to change. Here's why:
No proprietary hooplah, No special (bloated) software needed to open and the ability to view it on practically ANY device with a screen. Did I mention it's cross-platform?
Not so much of a new point but an addition to the above. Because these are plain text files, their sizes are incredibly small. I can write all my notes of all my semesters of school in <1MB. Plus, I can use Dropbox or even better, Github (or BitBucket if you want to keep it private) for syncing with home and office computers.
If you are taking notes and it includes formulas and you are using some tool built for generic project planning/note taking; best of luck with formula writing.
- The sheer number of output modes available
C-c, C-e and you have options to export as PDF, HTML, Calender and what not ! If I write out mathematical notes, I can create a nice PDF for my use and a nice HTML (including the nice LaTeX markup for others to see)
- The breadth of use/Versatility
You want to take math notes? It can do it. You want to schedule meetings, set deadlines, create TODO lists, do some GTD, maybe even some pomodoro. Whatever it is. org-mode can do it.
Have a problem? I can assure you that you won't have it an hour later if you look into the documentation or the mailing lists. The community is just too awesome. (Although this seem biased, I wish to reiterate that I used {and still use to a large extent} Vim for coding)
It's text based, it's emacs, it's fast. I read a joke somewhere that you can start emacs in org-mode and begin taking notes before your friend can say "Evernote". I personally love using it in emacs -nw in TTY mode so I work on one screen and there are no distractions and believe me, it's superfast.
- It's hard. But it's worth it.
After all, it's emacs. And no one can deny that emacs is pretty much raw infinite power in your hand. You can get started with org-mode in less than 10 commands and you'll do fine but if you invest in learning more, you'll never regret it.
Some things which are NOT true about emacs org-mode:
- It is made for programmers.
Programmers have an easier time if they already use emacs. A person using Vim but has been coding for 50 years will have as much trouble learning it as a computer n00b. Certain things are off-putting for n00bs (especially who are used to nice GUI interfaces of iOS devices) but again, it's worth it.
{Side note: It was more irritating to learn emacs after vim since I kept hitting ESC, :w every 2 minute only to find weird things happening}
- The era of text editors is over.
Not by a long shot. org-mode is 100% Open Source and Free. Even if the world stopped using text-editor altogether (I don't see this happening unless a Genocide of all *NIX users takes place), you can gladly keep using it. Also, org-mode isn't an unstable piece of open source software which has bugs every other day. It's VERY robust and for all things that normal people would do, it's practically unbreakable.
Side Note: For people suggesting Vim's org-mode (VimOrganizer or vim org-mode), my experiences with them have not been great and there are many other reasons but that's beyond the scope of this answer.