I had the Iamamsterdam card and entrance for this was included. The entry fee is 24 euros and I am going to base my review off this.
The 5D flight itself was brilliant. Really enjoyable. You will think you are going to fall off a few times and close your eyes thinking you will be hit a few times and there are other special effects with smell and water added also. Before you get into the actual flight there is a little bit of filler beforehand where they put you in rooms and there is films about the importance of water to the Dutch and they go through some maps of the Netherlands aswell. This is all just building to the 5D Flight. For a one-off visit I would say that yes it is probably worth the entry fee, especially if you dont know what to expect from the 5D Flight because it really is a surprise.
You have to get a ferry from the back of central station over to Buiksloterweg but it is free and only takes 3/4 minutes and there are two ferrys constantly working over and back.