Another newbie speaking.
I have followed DF mostly as a technical achievement -actually since Armok...it was wondrous but unplayable- and started playing/modding with the latest release.
To summarize, and knowing the shortcomings and in-progress cores, but referencing the current state:
Overall:
* Kicking a dead horse, the menus and such can get a facelift. But until everything is done, it's too much to ask.
* The ASCII interface is not too threatening for a veteran to roguelikes or games like ZZT and Megazeux, but even so the sheer variety makes impossible to tell what you are looking at "at a glance".
* Controls are strange. They don't resemble any other setting for any genre...it's pure original, but pure chaos.
* Everything sounds ugly. Descriptions are either too raw and no positive features are to be found.
Seriously how can we make elf jokes without them looking like damsels? No beauty is to be found, since the only traits are negative. This is fantasy medieval, it doesn't need to be so realistic about the old ages!
Dwarf mode:
To be honest, I barely touched this aspect of the game. (I know I am missing)
It is threatening in a way, the slow response and lack of information without reading or watching a tutorial, it requires a zen state of mind that, on its favor, makes it feel like embarking on a real adventure.
Adventure mode:
My real draw to the game, actually, but as many say, it's clearly alpha.
* Equipment management is bizarre and clearly a mere placeholder for the real thing. I completely understand it as coder (everyone does that), but, wow, it blows my mind.
* It makes CPUs explode. Although I understand this one well, too. To make it work well it has to work first.
The response lag is very high and chaotic (it has no rhythm so you are forced to key-wait-key).
* It gives way too many details. Wrestling is just incredibly difficult for example. Sure, it IS awesome to be able to throw someone from the back molar, using the right foot (or talon, I saw a harpy doing that to a goblin)...however, it makes "grab head with right hand" a 1000-entries long list. I guess this will be separated in submenus or something, so it doesn't worry me too much in regards of future development.
* Some descriptions should be dumbed down to avoid saturation. This is mostly about very verbose item names. Sure you need to tell apart items of similar materials (two leather items of the same class), but it can be improved.
* It's wondrous, but it feels too empty. The last version improves it a lot, but while you feel there IS activity -peasants move, monsters attack stuff and you find the mess during or after the action...there is life in the random world, but you can't do much about/with it (other than going medieval, solving quests, and exploring)
In a way there are games that are just that, but better looking, so it's a matter of time to see more stuff to do.
* Although it's on the core todo list, and related to the last point, there's little influence of the adventure in legends. That will change, so it's just a half-complaint.
* It was frustrating to see "strawberry bush" and being unable to pick the berries for later use. I could just set it on fire. It IS awesome but not the first thing you think about when seeing a bush with edible berries.
* Related to the last and possibly planned for the future, there's little to do in such a vast and complete world. Cooking, making potions, picking up herbs, building small structures even if laborious, digging, perhaps gambling, even setting up shops. Basically mixing some Dwarf Mode mechanics to be done as an adventurer and again, influencing the world further.
* Raising pets (as in war companions, food sources (keep your chicken around), or perhaps actual "pets" (within the limitations of the current AI, not asking for a pet sim...although Dwarf mode is a bit of a pet sim). For example getting a eagle egg protected by mommy eagle, and you hatch it and it's like a joined party member)...also further interaction with your companions, have them do stuff and help with battle and other feats like building or such. Make mercenaries that join you for money or goods...that kind of thing. More ways to make your own army to pierce the heavens. With horses, knights and racial stereotypes.
Right now your party is barely manageable, you just have them around or not, and can be killed without the played ever noticing or lost (like in some LP I am following where party members disappear into nowhere).
* Make your funds/value clearer. You don't really know how much things are worth, you don't know if the items you find are just junk or have significance. It seems only weapons and armor are worth something (might be true).
* Conversations mean nothing but quests and some minor background. More on that later.
* Combat is bugged but since it's probably being fixed as I write, not complaining.
* Cities and such work, but they are too crude. I prefer to spend more time at world generation and have villages with some roads and constructions, not random huts scattered around, but I am nitpicking now.
Modding and extending:
Despite my short time I already got to mod some stuff just for the kick of it. On its favor, despite bugged stuff and relative lack of documentation, it's very easy to mod stuff in. (stringdumps work but it's not pure detail)
* Conversation files are raw placeholders and you simply can't make much conversation with them.
* You simply can't make a "beautiful race". Like a nymph or such, they'd be subject to the description uglyfication since there aren't positive traits to mod with (as of now).
* It feels odd you can make a [MALE] [FEMALE] or genderless civilization prosper at all. Perhaps making races crossbreed or magically reproduce or randomly "evolve" from another creature, or simply spawn some every year...it'd be kind of awesome so you can get a tree city of harpies or demons gathering into some unholy city, or perhaps robots. Or like amazonesses, death by snu-snu and stuff. Can give a meaning to "baby snatching" races.
* Until more effects like magic or so are added, there's not much to do with attacks. Like a powerful wind creature like a bird or so launch a gust of strong wind at you and stuff. Right now it's just plain melee simpleness and some grabs.
* Nothing else not suggested yet.
All that said, I consider DF a masterpiece of "things a single game can do". It makes a whole world from the chewy core to the sky, and puts a respectable amount of work into it. Most things will be ironed out with time, but having a whole world to explore makes one wish more actions were available. I love/hate it soo much.