Only for the die hard fans of the series, otherwise rent it for a weekend.
The game is insanely difficult, yet not impossible. The cut scenes are really awesome, no doubt about that. All these are fine, but you don't buy a fighting game to see some nice landscapes, and a heavenly beautiful geisha that runs with her cute tiny white shocks on, and things like that. You buy it mainly for the action; kicking and punching. So simple! And in this field DoA 4 isn't very good. Characters move really quickly, ridiculously quickly, and the controls are not very responsive. Also, after a couple of hours the whole idea of the "alive" environments, with vases that can break to pieces, and baskets full of fruits that scatter all around, gets repetitive and inevitably boring.
It's not what you could say a bad game, there are far more worse titles out there, but it's not a very good one either. In other words, it doesn't quite live up to the "legend".
I give it a 6.5, and not lower, because it makes at least some effort to be unique in its, otherwise strictly defined, genre.