That right there sold me- no issues at all getting purchase orders at work and regardless of the OS I'm using I still have the same editor.
Case in point: WinRAR, anyone?
EDIT: Just to clarify, I like the pricing model too. I just don't think it works for software in general.
I point out winamp because it is similar in that no new features are unlocked after paying.
I think the nag dial is just about right between casual use/unlimited evaluation and I'm using this editor for real shit.
That is, it's not like, say, Chrome release where it's Dev -> Beta -> Stable. It is (was?) more like Nightly -> Dev -> Beta/Stable.
Of course, it is much harder to learn how to use Emacs properly (navigating with the keyboard, using more obscure commands, writing your own elisp... and so on). However, as everybody has pointed out, your text editor is probably your most important tool; it seems odd to be willing to put down some money on one but not willing to sit down with a tutorial and learn how to use something like Emacs well. Sure it might slow you down for a bit (it took me about a week to get as proficient with Emacs as I was before), but it's completely worth it in the long run. I've been using Emacs for almost three years now, and it's helped me do all sorts of things more efficiently than I would have with another editor.
Don't assume that people are flocking to ST2 because they're not aware of the alternatives. I'm very aware of them. For me, the advantages of ST2 over Emacs were worth the money and I'm glad I bought a license.
That said, I always keep the latest Emacs installed on my laptop and I could jump back into it if ST2 were to disappear off the planet tomorrow. I hope it doesn't, though, because I find ST2 more pleasant to use than Emacs and I hope I can keep using it for a long time.