Believe it or not this is harder than the bash thread, because it takes some brains to articulate properly (duh).1. Everything does two things. May sound silly. But, fireball does damage plus burning. GETINDARE gives First Strike and dodge. ENDISWAL breaks a wall and gives physical resist. List goes on, practically every game element in DD has a main effect and at least one side effect (that occasionally become more important than the main one). Now it may sound weird, but what this does is, nothing is ever totally useless (or, for that matter, nothing is ever straightforward). So you see that GETINDARE and play a Rogue? Insta-convert, unless, you want to benefit from increasing the dodge - which is, a much bigger benefit with a base dodge of 20%. List could go on, the point is, the game mechanics were designed quite well.
2. Combinations and synergies. So it's a bit of a bigger thing and it's mostly about game balance and variance, but I want to distill it down into a few sentences. So first you're discovering the game and you're like Orc Wizard, Gnome Sorcerer or Dwarven Rogue. Seems like the peak at the time. Then you're digging a bit deeper and you find workable stuff around Gnome Tinker, Elf Fighter or Orc Thief. Then you keep playing, and you find ways to ace Vicious with the Gnome Fighter, the Human Bloodmage or the Goblin Thief. After a while you could probably do any map with any class/race combination, simply by finding the synergy that may be completely un-obvious to players who don't look for it. It's not about skill elitism, it's about how well the game supports the learning curve - you find new synergies even after hundreds of runs.
3. Awesome devs and free expansion! Plus dailies! And great community! All the package *around* the game that makes it doubly awesome! (Yes I'm shamelessly praising everyone now, hope there's not a lot of blushing!
). Oh, and there's the Wiki, now that the new expansion adds a lot of content, and fixes bugs, and tweaks a number of unadvertised things, it will need again some work. Still it's an awesome resource. But I guess DD benefits from all the indie charm AAA titles and their studios pronouncedly lack. Having direct dialogue between the people whose passion is to design the content, and those whose passion is to consume it, without the freeloader in-betweeners whose massive salaries are justified by them sophisticatedly calling a "spade" a "heart-shaped surface-optimizing solution". 
) so as expected he completely misplayed the game and failed to showcase it properly, but none of that mattered, as soon as he hovered over a glyph and I saw its description I fell in love with the game and knew I had to buy it.
