One of the key differentiators of the game is that players have but a single life, death and all the ways it can come to you is final. This fact plus the chilling realism of the game bring about some interesting gameplay (going by what I have heard at least) - play is scary, an encounter could end your life. Zombies are highly dangerous, running is very wise - but other players represent the greater threat as their behaviour cant be trusted. Players turn on each other for resources like food and bandages and even just to eliminate the threat the other person may pose to themselves. This is a rather haunting display of how we may react if really placed in this sort of survival situation with our fellow man.
I am hearing the experience is incredible, a new level of gaming in much the same way as stepping out for those early moments in Everquest. We have been talking about what is needed to change games, to make them more alive and immersive - well here we certainly seem to have a vital step along a certain road. Many of the videos are of people who play alot of games and seem to be able to break things down into spawn points and loot tables etc - I think I would be highly immersed and it would be scaaaaary.
I like the way Tim explains the real leaps this game has made (is making) in his article 10 Reasons Why Day Z Matters on Trembling Hand. There is alot to applaud already for a game that is still in its early days.
[Day Z imagery via the Trembling Hand article]