White has a good position!

After 7...Nxd4 8.Nxd4 exd4 9.0-0 [of 9.Bxf7+!? Kf8 10.0-0 Qf6 is also playable]
9...Bb6 10.Bxf7+ Kf8 11.Bb2!? with good compensation for the pawn and an active game.
11...Nf6 12.cxd4 Nxe4 13.Bh5 g6 14.Bf3 Nf6 15.d5 with powerful attack!

I think in that way! :)

I believe the point is that after black defends f7 with Qd7 white can open up the center with dxe5.  Then after black recaptures, white's dark bishop comes to a3, attacking the queen, an increasing white's lead in development, which is complimented by the open position.  IMHO d6 is far to slow for black in Evan's Gambit, and it doesn't seem to do much to help blacks's position.  Black needs to develop, defend f7, and keep the center closed.  D6 doesn't seem to do any of these.

Also, with white's queen bearing down on b7, d6 does nothing to devolop black's bishop, since it is stuck defending b7 at the moment.

Is the point of 7.Qb3 black weakness on f7? Still, it's not so problem for black i think...

What is the point of the gambit?  Black's dark bishop is temporarily blocked off, but so what? Doesn't seem worth it.

with all the due respect for GM Tartakover, I think 7.Qb3 is not the best continuation for white