The Good: This version seems to run faster on the same PRINT_MODE than 31.x did for me. The fortress I built was not too much different from the ones in 31.x except that I let invaders come which I had not been doing.
The Bad: I can't generate large worlds anymore. DF crashes, or at least the OS thinks it has stopped, in the mid 200s. I was able to generate and play with a Pocket Region. That stopped at about year 30 by itself. I suppose this isn't so bad. I liked being able to choose from a wide variety of biomes but given that no site has every resource anymore, and all sites have magma, a Pocket Region seems to supply what I need. However, the difficulty in generating the Large Region is probably caused by all of the additional history, which I like to read, and of which there is little in 30 years.
The Ugly: Well I don't know if this was true in 31.x because I didn't allow invaders, but reclaim is a disaster. My fortress first fell to an invasion of goblins, with trolls, riding voracious cave dwellers. The trolls destroyed every building and the voracious cave dwellers appear to be undefeatable. When I returned to reclaim the first time, a forgotten beast which I knew was present and sealed in the caverns below the fortress was in the first layer. It killed all of my war dogs before my seven skilled axedwarves could get indoors. They killed it, at the cost of two lives. I lost three more to melancholy and berserkness. The other two were alternating throwing tantrums while they made coffins and installed them for the burial of the 70-plus previous residents, plus the traders who were present at the fall of the fortress, plus their own fellows. There were plenty of ghosts before it was done. A small wave of migrants saved the day before one of the two could go berserk and kill the other. It looked good, until the first Vile Darkness turned the loafing ex-invaders into enemies again. I had disarmed and disrobed the trolls and most of the goblins, but there was nothing I could do about the four voracious cave dwellers. The fortress fell again, with another 65 or so deaths mostly caused by those. I was willing to try, try, again BUT when the second reclaim team showed up there were TWO forgotten beasts in the first level along with the two surviving voracious cave dwellers and a couple of stray goblins who had been hiding outdoors when the others were being disarmed. There were none present when the fortress fell. I consider this foul play, and wonder if the formula is one forgotten beast for every reclaim effort. Do we get six forgotten beasts on the sixth try? In the old version, 40d, we used to get a reclaim party sized to the difficulty of the reclaim, but we just get the same seven now no matter what is waiting. I can mod the voracious cave dwellers into death if nothing else works, but there is nothing I can do with multiple forgotten beasts and only seven dwarves.
More Uglies: My military had a distressing habit of dropping all of their gear when they were told to stop killing an enemy they had already killed. Instead of returning to their barracks and continuing training, they shucked everything on the grass and ran for the fortress, whereupon a Giant Kea stole all the best gear. I finally got that stopped by making them go to station after a kill, so that they were at least indoors if they wanted to ditch the uniform and go AWL instead of training. I had quite a few Dwarves killed by Everything-Men-and-Women. I had many migrants show up with no work set despite their listed professions and lost animals to starvation because a listed butcher wasn't really one. It's easy to say that you should examine every migrant closely, but when waves of 20 or 30 are coming in every season that seems a bit unreasonable.
And yes, it is an alpha.