On a laggy setup, or a fort facing fps death, you can regain some playability through fastdwarf.. Of course, I'm hopelessly addicted to fastdwarf now, and feel like smashing my skull open watching dwarves saunter around at their vanilla speed.. I also use autodump to stockpile huge amounts of stone and wood so dwarves aren't busy hauling (and pathing to) it all for the next year..
If DF had a couple of game-speed modes, similar to what the Sims has, and assuming that amping up the speed wouldn't triple the lag, then I'd just use that.. I don't use fastdwarf because it makes them fire crossbows like semi-automatics, or slash away at enemies like berserkers, or do ten times the work for the same amount of food and drink.. I basically set up safe 'creative mode' worlds by turning off evil zones and demons/night creatures/bogeymen/megabeasts/titans (I do leave werebeasts and vamps, though..), remove all the caves, cap the world to a single playable civ and then I'll run the world for 9999 years.. Occasionally you'll get a world with no necro tower but 10+ necromancers all living in the fort :| But they still count as a living civ so you won't get an early king-dwarf dropped on you..
Its effective against that general.. melancholy?.. that DF players occasionally suffer when confronted with setting up and fine-tuning a whole new fort, for me, especially with the understanding that you could pull the lever a second too late and lose a young fort to a single zombie..
On it being 'cheating' or 'undwarfly', when these kind of options are widely available (as with Minecraft) I always assume that there's at least a chance that a megaproject was aided by non-vanilla means, though I do respect people who achieve their goals through vanilla play.. I always say so when I use fastdwarf or other exploits (like setting up my magma industry by creating it with 'liquids' command), and always believe community members when they say they've done something in vanilla-only.. Not to mention that any seasoned vanilla player knows what can and can't be accomplished in a given time period with legendary miners..
I embarked with all seven dwarves with 5pts in mining and steel picks and channeled a massive entrance all the way down to the first cavern layer (started with a 80x80 square and channeled out the area inside it each time so it'd slope all the way down, and when I finally reached the cavern the hole was around 20x20..), and completed it in a little more than a year.. Normal dwarves would have suffered to half-complete the first gigantic designation in a year, much less the layers and layers after it :>