Dwarf Fortress is much better then adventure mode imho. Adventure mode is fun too, but Dwarf Fortress is simply brilliant. This alpha version game just hit alpha a few weeks ago, but there are lot of topics on various message boards with 200+ posts about the game already, and everyone is amazed, that how complex and deep gameplay it has already. Have you guys seen the future development plans? If those will be added...frankly I dont think that I will stop playing this in the next years.
I think the only weak part of the game is the ASCII style, many people won't try it, because they don't like ASCII. I've played with many roguelike games, so I have no problems with it, but a graphical expansion would be nice for the game. When the major elements and features will be added to the game in the future, Toady might add a tile based engine, at least I've seen this on IRC like 2 days ago, they were talking about that. However that won't happen just in like 1.5-2 years. Tons of work to do still [check the dev list], and only 2 people are coding the game.