Obviously, it's not as good to get your D3 in supplemental form. However, many of us just can't get enough sun so we NEED to take it another way! I'm sure some D3 supplements are better than others, though. This seems just the way of it when it comes to supplements.
If there are D/L problems with the vitamin D3 people get, I suppose one would assume it was about 50/50? (I have NO IDEA... I haven't read enough about it... so I don't even know what its molecular structure is ). So, from that theory, maybe 50% of the supplemental stuff is useful, and the rest isn't (harmful though?? who knows!).