Four of the new blocks that have been added to the game include andesite, diorite, granite, and slime blocks. The first three, in that list, are new rocks which can be crafted into "polished" versions. Andesite and diorite look similar to gravel and cobblestone, while granite looks almost like dirt. All three are very abundant and easy to find. So far, I have used all three polished versions to create a house in my new world. I have not yet had any experience with slime blocks, but I know that you can bounce on them. One of my favorite YouTubers has a video regarding this new update, which I recommend watching (http://youtu.be/Q9ykTDAFl7E?list=UUP6f9x4iXk3LH8Q1sqJmYPQ).
Sheep now drop mutton, which can be cooked as another food source. This update also introduces bunnies. They are adorable and come in a variety of colors and designs. They can be bred with a variety of items, but only carrots will make them follow you. They also drop meat, which can also be used as a food source. There is also a slight chance for a "killer bunny" to appear. This bunny has red horizontal eyes, while the tame ones have eyes that are vertical. This "killer bunny" is clearly a nod to Monty Python and the Holy Grail. The end of the following video gives the best strategy for when encountering this new "killer bunny" (http://youtu.be/92gP2J0CUjc). (Hint: Run away!)
There are now also ocean monuments which are underwater and apparently filled with water. I have not yet found one, so I can't quite report on it. I know that these monuments contain guardians, which are a new mob. There are also new blocks within these monuments including prismarine and sponges. For more information visit the wiki (http://minecraft.gamepedia.com/Ocean_monument).
Finally, I think the most important part of this update is that the game's performance has been greatly improved! When I got my new PC many months ago and played Minecraft, I was impressed by how far I could see, but still disappointed in how long it took chunks to load. Since I've been playing with this new update, I have not had any issue whatsoever with chunks loading. The only chunk loading I noticed was initially when I spawned in my new world, but that's it! Previously, while walking around, I had to wait for chunks to load, I no longer have to wait at all! There is also a new option in the video settings, "use VBO." This feature apparently gives about a 10% increase in performance when set to "on," by reassigning some of the processing from your RAM and CPU to the GPU. For a little more information about this setting please see the following link (http://gaming.stackexchange.com/questions/177257/what-is-the-use-vbos-setting).
Now seems to be a great time to get back into Minecraft, if you've been away from it for a while. There is still much that I have not covered, so I recommend checking out the wiki for the full release notes.