This will be a bit long-winded, and I apologize in advance for that. I just thought I should share my experience with Dwarf Fortress, because I've come to realize that it hasn't been the same game for me consistently throughout the time I've played it. This is the story of how I came to play DF, and the underlying tale of what made it so appealing to me.
I started out reading a Something Awful LP, well-known in the DF community, about a fortress amusingly named Boatmurdered. It painted a picture of an increasingly bleak fortress where anything could happen at any moment to turn the whole community upside-down, and it was an experience just to read it. By the time I completed my read of it, I knew I had to try Dwarf Fortress.
Like any complex game I delve into, I first researched the game's workings before I even booted it up. I learned as much as I could tolerate about how it worked, about what every workshop did, about how each career functioned, and so on. I knew more about DF before I first loaded the game than most people know after their fifth fortress, even. There were a few concepts I didn't grasp since the DF Wiki didn't explain them in a way that makes sense without seeing it in person, but I'll explain that later.
When I first genned a world and settled in, I was of the mindset that this game was like it had been when Boatmurdered was written: all on a single 2D plane, with hell erupting every few moments. I'd already built in my mind a strong defensive 2D layout for my fortress, and set about creating that vision right away. I learned before long that the game I was playing, however, was not the same game that Boatmurdered had been set in. This was a new version, with new rules, and I was entirely unprepared for this fact.
To say my first fortress was a failure would be an understatement. I never set up a smelter or a metalsmith's forge, since I hadn't found the (nonexistent) magma river to do so at. My Dwarves weren't starving (I figured out farming before I even loaded the game, having heard horror stories of forts dying of starvation), but they also had miserable existences that were devoid of any meaning. I knew I was missing something critical here, but I wasn't sure what just yet. I abandoned that fort before the first year was over.
My second fort fared better, and I got more done, but still something seemed wrong. I wasn't finding much metal overall, for one thing. For another, I still couldn't find the (still nonexistent) magma river. Though I had found a lovely magnetite cluster (which still sticks out in my mind, since I'd never seen magnetite clusters before then, and I didn't really understand how the metal distribution system worked then). It was in this fortress that something strange happened: a Dwarf who was set up with the Hunting labor seemed to have disappeared off to some part of the map THAT DIDN'T EXIST!
Or so I thought at the time. I had read about Z-levels on the DF Wiki, but I hadn't really understood how it worked. I was confused for some time about this wandering Dwarf who seemed to be on another plane of reality entirely, and finally I accidentally figured it out while trying out key combinations when I mashed , and . while holding Shift. Entire PLANES OF REALITY revealed themselves, and I came to fully realize what Z-levels meant. This was not the Dwarf Fortress of Boatmurdered's time. Oh no, this was a VERY different game.
The entire experience changed after that. That was the point at which I disabled the background music as well, and it has as a result inexorably linked my time in "2D" DF to the game's looping main music, while my time in "3D" DF has been devoid of any musical consistency. Anyway, from that point forward I began designing in 3 dimensions, and immediately sought out an ideal site. Unfortunately, I couldn't find anything on my own, so I turned to the DF forums and downloaded Smata Sagus. But Smata Sagus was an ideal site only in earlier builds of DF, and was now sub-par.
But Smata Sagus was also my first introduction to another component that also changed the experience: chasms. I had never seen a chasm before that, and it gave me a chill to see what I dubbed "the fingers of the mountain" stretching out with an endless void at the bottom. That, the cave spiders randomly leaving webs all over, the brook freezing in winter, and the fact that my Dwarves had a bedroom RIGHT NEXT TO A BOTTOMLESS CHASM, totally revitalized my fascination with DF. The mystery was renewed, and 3D DF was again an experience like no other. Then I found Dwarf Heaven, and started building there. There, at the height of the mystery, the veil was lifted when I found out about Visual Fortress.
Being able to see my forts in 3D changed the equation drastically. It wasn't just mutli-planar 3D I was dealing with any more; it was cohesive 3D. It was layers of 2D building up to make a full 3D experience. Before, the 2D levels were segregated from one another in my mind, unrelated but linked through stairways and ramps. I was entranced, and immediately set out to build mega-constructions in this new environment. Before long, that became the key lure of the game for me, and I basically disabled everything that didn't have to do with mega-constructions: no invaders, no cave-ins, no economy. Just pure, uninterrupted building. The game had become glorified digital Lego blocks to me, I realized later.
I'm starting to drift away from DF again. The mega-constructions aren't as fun to make any more, and I don't really care for the wildly unpredictable battle system (mostly since I have legendarily bad luck and can somehow manage to lose 20 Champion Dwarves to a dozen Kobolds). I want to enjoy the game again, but it's just losing that spark.
And yet, every time I listen to that music, I remember my misguided 2D experience, and long for those days when DF was mysterious and awe-inspiring due to that feel that I could never see what was around the next corner. I want to return to that point in time, and that understanding of the game (incomplete though it was), and live the experience again. It sounds like the next version will help a bit in this with its caves, but what I'd love to see is the old single-plane 2D DF brought back with all of the improvements that the 3D version has, while maintaining the things that made the 2D version so charming (like the magma river).
tl;dr version: DF has changed for me every time I learned something new about how it worked, and in spite of that, I'd enjoy a return to 2D DF with 3D DF improvements in place.