Hi Zach, thanks the efforts! If you are still working on gathering and prioritizing feedback, here is my experience as a new player who knew exactly what DF was and wanted to play it because of its reputation as difficult to learn and insanely complex.
1. Military screen. Anecdotally, I bounced off this screen for an entire year. It is extremely confusing, different from most other screens, and tiny. It's also a core part of the game. You have to read everything very carefully to avoid making a mistake. You also have to write down the dwarves you want to draft, because there is no context or stats shown in the citizen list. My wife just had a squad training for an entire year to be wrestlers because she didn't know she had to assign them a uniform. I knew (from reading the wiki) that I had to assign my first squad uniform, but couldn't see how to do it, and then kept screwing it up.
2. Likewise, the "squads" menu is just not very discoverable. I had to google how to make my military do anything, or even start training.
3. I could not find the labors menu and dwarf statistics after searching for a while, and just used Dwarf Therapist. Now that I know where it is, there are some issues that might be easy to fix: There ought to be a way to switch from "View Thoughts and Feelings" to the z "Status" menu. You should be able to access the z status menu using the k look command. There needs to be a way to view "big picture" of dwarf skills and labor settings, to find under-allocated dwarf to give a job to, or a strong dwarf to draft into the military.
4. Marksdwarves. Something any new player will want to try, and be frustrated by. In short: Bolts in bins being locked to one dwarf at a time, the aforementioned military screen, the many steps needed to create a working archery range, crossbows being used for melee even though ammo is available, etc.
5. Being unable to find metal. This can be pretty frustrating / confusing. I think any new player would expect to be forging amazing things out of metal. I was pretty bummed in my first fort when I realized all I had was zinc, and I would have to start over if I wanted to be forging awesome metal weapons. If you add some kind of feature to help a new player choose an embark, I would recommend including some metal they can make weapons out of.
6. Inconsistent menu semantics. Sometimes an option is showing what it is set to currently, sometimes it shows what it will change to if you press that letter. Yikes.
7. Menus that don't provide enough context. This is very common, and very frustrating for an advanced beginner. For example, with the new guild system when I go to make a new location it doesn't highlight the guilds I've accepted petitions for. Additionally the locations in my fortress are listed by name only in many places, even though I cannot possibly remember whether the farmer's guild is the "Guild of Hail", or that the tavern is named "The Rattling of Cages".