I have had the 3D box for about 9 months now. I have a HDS12. I pretty much have the same opinion as Mr. Sherman above. The 3D is useless in the depths that we need it to be useful. If you pay attention to the videos you see advertising it, you'll see it's in 60+ feet (usually salt water). I have spent a lot of time trying to adjust and tweak it and it just isn't beneficial to me.
With that said, the transducer that comes with the 3D box (maybe the total scan xducer) is much better than the older side xducer. It is not only clearer but in shallow water, side scan will still read. With the old transducer, when I got in less than 10' of water, it wouldn't read much past 20-30' out. This new transducer will read 60' out in 5' of water.
Is it worth the $1k? No. I believe you can buy the transducer separately now for $500. If you are a serious fisherman, I do think it's worth buying the transducer.