All right, so I'm testing two box objects. One is standing fixed in a position and another at the beginning of the program goes to the first one. And at the end the latter should stand completely over the first (so the center of both is equal).

Here's my method in the Object class:

void Object::moveTo(Point _p) { // _p is always the center of the other object we want to go to

    // adjust speed, don't worry it's not important here, I guess
    if (current_speed == 0)
        current_speed = speed/16;
    else if (current_speed >= speed)
        current_speed = speed;
    else
        current_speed *= 2;

    // we want to calculate the new center of the
    // our object (the one that run this method)
    Point center;
    // distance(x) calculate the distance between the center point of the object and
    // the x point passed
    if (distance(_p) <= current_speed) {
        // we don't want shaking things!
        center = Point(_p.x, _p.y);
    } else {
        // move diagonally
        center.x = getCenter().x + speed*std::cos(angle(_p));
        center.y = getCenter().y + speed*std::sin(angle(_p));
    }
    // since we draw sprites by the top left corner we need to convert
    // the center point to the correct top left point
    center = toPosition(center);
    sprite.setPosition(center);
}

This is what happens: http://youtu.be/Ngra3FXFe0A Why is that? Showing the distance at where is stops it usually keep going from 15.xxx to 16.xxx and I don't know why.