I've got a new 4x4 embark. It's got 3 squares of haunted tropical savannah or something like that. It's also got a necromancer neighbor and should attract goblins as well. The main thing is that I have no water topside, no aquifer and very few trees. I've found the first cavern level and it's almost all water, in fact I've only just spotted a few areas on the edges that actually have land. Oh, and its a deep level, about 11 z levels, with very few large open spaces, and it begins about 40 z levels down.
So far all of my forts have been topside, in the first 10 z levels or so, but I'm considering building my fort under the first cavern level. That would make any projects with water a whole lot easier and put me a lot closer to the magma. I'm not interested in turtling though and would probably maintain some sort of outpost up-top with some barracks, a trade depot and some stockpiles for trade goods etc. There's also platinum and tetrahedrite that I'll need to dig into. I haven't done much exploratory digging so there might even be coal, which could change things.
I guess I'm wondering what others experiences with deep fortresses are. Was it more fun/less fun? Got any brilliant ideas of what to do or not to do? I'm thinking I'll probably use minecarts for the bulk of transport up and down from the surface.