I'd say DF has a pretty steep learning curve - I must have been playing a month or so now, and with healthy doses of help form the good folks on the boards here I've finally got a fortress that's managing to sustain itself with ample booze, food, bedding, healthcare, clothes production and even a metal industry.
Having learned how to use emergency burrows, I avoided the fall of my last fort, which was all my civvies running outside and getting killed by an ambush. This time, my hunters single-handedly killed the ambushing Goblins and I nicked all their stuff.
And now? I've just hit my first ever full-scale Goblin siege, and it feels like I've suddenly discovered the true excitement of the game! I really put some planning into my Fort's surface protection and it's totally paying off. I filed down all the hill ramps so that there's only a few routes to my mountain entrance, then lined them all with curtain walls, filling deliberate gaps with traps.
So far I've just watched 6 Goblin swordsmen get absolutely mauled by Goblin-made Large Daggers and Morningstars (a most satisfying use of weapon traps!), the other 10 or so have just breached the first curtain wall...and blundered into my courtyard of serrated metal discs with spectacularly limb-scattering results.
If any survive that, they'll then have to cross through my caged/giant-axe'd entrance hall (engraved tastefully with pics of Goblins being slaughtered with crossbows), over a retractable spike pit, past a chained Giant Kea and then a bunch of enormous corkscrews
So yeah, I continue to be amazed at the depth the game has. Learning to manage your fort and keep it running through the day-to-day seems to be only the very beginning of the game.