Is this opening good?

Ok one last question Javier, is this opening good for white or black?
1. e4 Nf6 2. e5 Nd5 3. d4 d6 4. c4 Nb6 4. f4?!

That's the 4 pawns attack against black's Alekhine defence.
Personally, I wouldn't recommend it for white, no. A large centre is not necessarily a strong centre. In fact, in this line, white´s centre is very hard to maintain. I would only recommend this line to +2200 rated players who know the theory very well...