Played latest version, being a new player having migrated to DF from Minecraft. I wanted an in-depth game that I could play without feeling the need to include too many mods. Mainly because for all the evolution in and standardizing of modding that minecraft has gone through, most still fall prey to a few simple key issues, here are the ones I felt MDF has fallen prey to:
First - documentation. I put this first because it is THE most important thing. The manuals were very lack luster. Also the less you have to consult the MDF manuals the better. In-game documentation, or simply intuitive reactions/building design are best. EDIT: One big thing I noticed, is the wiki for the mod. Vanilla df has the player base to support a wiki, sadly your mod does not. Most pages are blank, still. Many pages are missing. Documentation will most likely have to come from you. Sorry if that sounds harsh, but that's what this thread is for, right?
Second - less is more. Especially in a game with DF's already enormous depth. It's grating to see mods that force content and ignore what's already there, feels like the modder is trying to fit a square in a round hole. My favorite mods have always been the ones that expand on already existing elements, or provide alternative routes to accomplishing goals, for example one thing I did really like was new way to get fuel that used an existing building. That is also an example of how to eliminate some of the need for documentation as the player will discover it naturally without making new buildings and there's no mystery around how to accomplish it.
third - incomplete or buggy content. Remove it, all of it. If it isn't done, but you need feedback, a dev branch would do that right? Most would want a clean, complete feeling mod. It would also ensure a more dedicated tester base, as they would be volunteers, not frustrated fans. I might feel different about this except that I'm not a teenage gamer anymore

, anything that feels rushed or not at least semi-professional just makes me go into a cane waving frenzy lol.
I'll end this with a few of the things I enjoyed most about the mod:
First and foremost, the races. You had me at gnomes.
Second - alternative power and expanded machinery and traps, electricity etc. The extra automation
third - the different ways to interact with the world at large with raids, telegraphs etc, adds nicely to the immersion.