So I've got two forts going on right now, one on my stream and one off-line. Both are modded, with added enemies via FortDefenceII and some RAW tweaks.
The stream one has some decent physical defenses in the form of a tall wall, and is in a reasonably nice area savagery wise (High, Neutral). Weirdly, the river is frozen until mid-summer, unfreezes for a few weeks then refreezes again, but I didn't settle in a cold region that I recall; a couple of ponds on the south end of the map however only freeze during the winter.
It's run into a few problems: No anvil. I didn't embark with one, and have had no dwarf merchants in 3 years, just human and elven ones. Hundreds of bars of metal and charcoal ready to go! It also means my military is barely even adquate. 10 Dwarves with decent skills but only 1 has armor and 4 have weapons.
Now, strangely.. I had some "Friends of Nature" ambushers come onto the map.. that are ELF LOVING DWARVES. Heretics, of course. They even use BOWS for Armoks sake. I also think one of my militia might be a spy... in a recent strange mood he made a BOW.
For my off-line fort I settled in a Good area, which Ive never done before. No unicorns yet, sadly. I'm trying out a few new aesthetic things in my design, mainly in the area of bedrooms. As with the first one, it has a tall above-ground tower for defense (with a lip to prevent climbers, of course), but I remembered to leave space for a moat of sorts around the edge. Its quite a bit newer than the stream fort so less has happened.. but they DO have an anvil. I'll post updates if I remember!