Well to be more specific- I'll discuss some of the big changes in the new DF2014 release.
Garden vegetables and trees:
One of the first htings you'll notice is that trees are multi-tile now and rather tall. They have leaves and flowers and berries! The first two are worthless, but the fruit can actually be picked in the summer! This is a new mechanic where certain plants/trees are only harvestable during a certain time of the year (a few weeks into summer, typically). You can build a ladder at a carpenters workshop first and set up a "plant gathering zone" from the activity zone menu (i-draw rectangle-g?) Draw these -under- the trees you want picked. Herbalists will then grab the ladder and begin picking fruit from the 2 z-levels above him off the tree. Combined with multi-hauling, dorfs can pick staggering amounts of food in this season. I've had 3-4 untrained dorf from my starting 7 pick several hundred during the first summer this way. The fruits are edible and usually brewable, but you cannot plant their seeds. Some seeds (like the tropical rambutan) can also be eaten, but most are just junk that eats into your global seed cap. Sadly, nuts are not edible. So while you can have pecan and almond trees, your dorfs won't pick them. The most interesting trees are probably olives though. You can most definitely press the olives into oil+olive pumice. The oil can be made into soap or further cooked into meals. Garden vegetables only fruit at the same time as trees, mainly, but usually have edible growths year round as a stop-gap method. Berries are the easiest example of this- even the old strawberries will only yield (brewable) fruit during hte harvest season. More plant-fiber and flour crops were added as well. Of particular note is hemp, which counts as a flour, textile, and oil-seed for pressing. Hilariously, you can store hemp flour in hemp bags. Then make hemp-soap. These are still buggy though, as anything described as having a -pod growth (beans and nuts mostly) are still worthless and un-gatherable.
Multi-hauling. I mentioned this briefly above, but dorfs will no longer hall just one small item at a time. This mostly revamps herbalism, as I've easily seen a single herbalist carry over 100 plants at a time. In an area of thick vegetation, I've seen proficient (skill 5) herbalists bring in 130+ plants in about 2 weeks of game time. I've started forts and gone crazy on herbalsim. Between multi-hauling and trees I believe I was pushing 10k plants collected in the first year? It was at least 6k. You'll still never see a dorf pick up multiple barrels or stones, though.
Thoughts and stress revamp. Dorfs have more nuanced personalties now, or at least the nuances mean more. A dorf that loves fighting and violence will actually get pleasant thoughts sparing and killing. Dorfs that love commerce get warm fuzzies if they get to trade as the broker. Conversely, dorfs that hate commerce hate being brokers... Dorfs that place a high value on crafmanship get more pleasant thoughts from viewing masterwork statues. Dorfs can handle stress differently too. So some dorfs are neurotic messes and break before others, however "breaking" happens much slower. Breaking doesn't mean a tantrum though, but actual death-by-insanity. Dorfs can go beserk (irreversible tantrum), catatonic, or full blown crazy (strip naked and run around gibbering). In all cases they stop eating and wait for death. However, stress builds up more gradually and can be buffered by positive stress. A dorf won't just immediately snap into a tantrum when their kid dies. They'll just do that next season unless you seriously intervene. You'd really need to read more (on the wiki) and see this one for yourself. Just try to keep an eye on your mayor/expedition leader more. Dorfs that visit the mayor are doing so to vent steam. If they have more than one meeting with the mayor they are likely about to blow a gasket. You'll need to stop and examine their thoughts screen to not only find a problem, but look over their preferences for the best solution to cheering them up. Typically bigger, blinged out room can't go wrong- just try and match their item preferences.