Just finished playing a new world for 10 hours (ish, I did some boring domestic stuff IRL too).
Obviously, like has been said, there doesn't seem to be a purpose to levelling up. I'm still trying to avoid dying however, I just like how long I've gone without dyinging, and how slowly my exp bar goes up now (haven't died yet).
Explored quite a bit. Vines don't do anything as far as I can tell, they don't seem to drop anything. Hopefully grappling in the future. Lots more mushrooms, in swampy areas in particular (places with water, trees and vines everywhere).
Met a a few Endermans (Endermen?), they stare at you, disappear, then appear behind you. If you have your back to something, they'll stay disappeared for a while. That's so much as I've worked out. Without looking at a wiki or something I'd say they do 2 hearts of damage per hit? So they aren't anywhere near as final as creepers.
Lighting changes are welcome but I think there has been a reduced effective range for torches in regards to preventing spawning. However the ambient glow they produce is very warm and satisfying.
Chests open. It's a little animation. It's alright?
I've found a few caverns / underground canyons / ravines (?). If you can traverse them, they're rich in resources and dripping with cave systems and stunning vistas. Stepping out of a cave onto a single row of stone blocks to be met with the vast imposing parting of two huge faces of rock and lava, is quite something. Making your way down them is inelegant if you can't find a cavern system, or come out on top of one with no alternate routes. There's always another way in, but it's more trouble to leave and look for it, then just shift + build your way down.
Cows and chickens drop meat now. The cooked porkchop image has changed to better represent the colour of a cooked porkchop, and now cooked beef has the old one. They always drop meat as far as I can tell. That's a nice realistic change.
As people have said numerous times, you need to eat to remain "healthy". I don't know what happens if you starve, I have yet to. You do move slower and don't regenerate (at all or as fast, again, not 100% sure, I keep myself well fed =P) if you get hungry. Food doesn't heal you.
It looks like the monster spawning next to bed thing has been removed? It hasn't happened yet anyway, but maybe it has to someone else.
I haven't found a village yet, haven't been looking for one. I've spent most of my time in the ravine / caverns, searching for diamonds. It's been fun. I'll attempt to find my way out tomorrow and make for some villages.
Oh the new biome code really stands out. The worlds are beautifully pieced together. I went from spawning in a really dense forest, to leave onto a meadow, complimented by light rolling hills, with a few steady rises covered in trees. A little further along (after the first night inside one of the bigger hillsides), I came upon a large body of water and some swamp. It was all superbly pieced together. Look forward to excavating / climbing a mountain when I find one.
I do hope Notch takes one or two more good ideas from Terraria, in so much that we see randomly placed, but designed / scripted content. A "boss" or NPCs with simple dialogue and interface would really flesh out worlds.
Finally, I can't wait to see what he does with experience and levels. It's an exciting future =D