After nearly nine years of using jEdit as my primary text editor, I have switched to Vim because of its lower computational requirements, its ability to function in a text-only environment (256-color terminals and terminal multiplexers for the win!), and its efficient modal approach to text entry, navigation, and manipulation.
But what really spurred this sudden change? It was an inferior CPU.
I bought an NVIDIA ION system with the Intel Atom N330 processor last year and built a silent, low-power desktop (33 Watts total!) that could still play HD movies. I don't play computer games anymore so this was sufficient for my programming needs, or so I thought...
Unfortunately, this new system was sickeningly underpowered (CPU wise) as jEdit literally began to crawl. It would lag when displaying text that I had typed on the screen, and would pause momentarily before scrolling the text buffer to the next or previous page. This was clearly unacceptable!
Luckily, I was reasonably comfortable with Vim because I had been using it to make quick edits (whenever I was in a terminal) for the past six years. So this time, I decided to seriously learn it, once and for all.
After a few days of self-reprogramming, I had a heavily customized Vim with easier jEdit-like shortcuts and the ability to install Vim plugins neatly. I had completely switched to Vim.
Now I truly am a terminal dwelling, modal editing Linux geek! :-]