Which ones?  I did not see anything that looked new.

Some links in this KVR thread.

That link discusses the new Analog Dreams/Ethereal Earth/Hybrid Keys libraries that are part of the full Kontakt 6package.  I don't see any hint of them in the free K6 player.

 

msorrels
In fact you might have a hard time even telling you were using 6 instead of 5.  The differences are that minor.

The biggest thing I noticed was that my quick links were not ported from 5 to 6 player.
 
I have made some of my own instruments and scripts, and the Creator Tools could have been a selling point for me if I thought I was going to have that much time to mess with that in the near future. 

Sorry, I thought we were talking about the full version. I've never used the player. Does it even come with any libraries?

There is a free collection to download for Player. When you opt to download Player you receive two emails. One with a link for Player and one for the free library.

When I installed Reaktor 6 player (having the full Reaktor 5) I encounterd an issue in Komplete Kontrol where KK insisted in using 6 even thought 5 was still installed. As a result all the non-regestered third party and free content caused it to go into demo mode. I uninstalled it and continued to use 5 until I upgraded Komplete. 
 
I wonder if this is the case with Kontakt 6 Player? If I installed it would be for curiosity only but I suspect it could be more trouble than its worth at the moment. My current plan is to wait until I upgrade Komplete.
 

If past history is any indication, Kontakt 6 should peacefully co-exist with version 5. At one time I had four different versions of Kontakt installed and never had an issue, as long as I didn't get confused about which version I was inserting into a new project.
 
The Kontakt player itself, AFAIK, is self-contained and does not install any other DLLs that might result in a version mismatch. I've just now verified that assumption with Dependency Walker.

I think the issue I had with Reaktor player was only in Komplete Kontrol and is patch browser. If a patch required Reaktor, 6 Player was launched, and if it was a non-registered patch in demo mode.

Outside of KK the two versions co-existed without problems. Unless I have a very compelling need I won't be installing Kontakt 6 Player.