I play DF, check the dev updates daily, and post somewhat regularly on the forums. It ate my entire summer break because it is simply that awesome. Currently though I haven't played it in a few months since I don't want to get too burned out right before the next amazingly epic release. Over a year and a half of Tarn Adams dev time in the update.
As for graphics, I personally think they would detract from the overall feel of the game. The game thrives on imagination and emergent storytelling, neither of which have as much leeway when the graphics are crysis-like. IMO anyone who is put off by the graphics needs to re-look their gaming philosophy: do you want the latest shinies which you will toss in a month or incredibly deep gameplay which will last for years? Also, read the Hall of Legends stories. My personal favorite: http://www.bay12games.com/forum/index.php?topic=15572.0 as well as the more infamous Boatmurdered: http://lparchive.org/LetsPlay/Boatmurdered/
The learning curve is more of a learning cliff face, but after a week without closing the wiki, you will get the hang of it to the point where eventually you will have the hotkeys memorized for most tasks. In general the UI sucks and really doesn't do the rest of the game justice. But once you get over that fact and learn to live with it, you will have an awesome time making cat biscuits, building magma cannons, tossing goblins off a 10 story tower into a 20 story pit, and depressed homicidal dwarves who send your fortress spiraling into oblivion. And remember, the game's motto is "Losing is Fun."
On a side note, the Creative Projects sub-forum is crawling with programmers and/or people who love insanely detailed games, and as such is always full of win. Including of course my own little thread detailing my exploits while teaching myself DirectX 9 http://www.bay12games.com/forum/index.php?topic=47915.0
Edit from a day after initial post: YAY!!! Early test version of DF2010 to be released next week! And although as buggy as the first iteration of a Stardock Beta, it shall be quite fun to play.