Key Features include:

Improvised Hunger ( You can eat anytime, Regeneration is much slower , and if you dont eat , you will instantly starve to death)

Torches have to get lit by a matchbox (or flint and steel) and burn out after a while

Randomised structures generated all throughout the world

A lot of more weapons

Item physic overhaul

Audio and Visuals are enhanced

Spawners now have a limited amount of mobs they spawn before they are un-usable

Animals Are more realistic

Doggy...

Enhanced dimensions and Biomes ( Biomes look MUCH more beatiful and are more realistic)

Camels. Yes Camels

Lots of Paintings

Herd Mentality on animals (if you hit 1 cow for example , all the surrounding cows will panic and run for their lives)

Features from console and PE are added

How to start

The Start of the Game as of 1.7 Beta , Is Vanilla but there is a lot of realistic aspects to it . Food will be much scarce and you will have to scavenge it , Livestock will have to be maintained or they will starve , Torches burn out and much more for you to find out ;)

Qoko