SACD & DVD-A audio seems to be improved. I can't comment on PQ as I never used the 2300 for DVD's and haven't used the 2900 for DVD's also. Early stages of testing. The jury is not out on this one yet.
I can't do a A/B comparsion but my swap was a day a part and my memory was as fresh at it will get. Overall the 2900 is much more pleasurable to use on the audio side and it sounds great. I have not tested the video yet.
Another thing that I really like about the 2900 is the consistent "Highest & Best" use of the media that I throw at it compared to the S2300.
When you setup the 2900 you indicate whether you have multichannel or two channel SACD. What does this all mean? If I slip in a hybrid disk that has 2ch PCM, 2ch SACD and Multichannel SACD layers, it will start playing the multichannel SACD layer automatically. The S2300 on the hand is two players in one, joined at the hip. You have the DVD mode & the SACD mode that are switchable on front panel or the remote. If you happen to have the 2300 switched on the DVD mode and slip in a hybrid SACD it will start playing the PCM stereo layer. If I had the SACD mode set at two channels and then slipped in a dual layer SACD that had both 2 and multi-channel it would play whatever mode it was playing last which could be two channel This was all kind of annoying as I always had to be conscious of what I was doing with 2300 and had to basically preset the player before I stuck a disk in it. The 2900 is very seamless that regard.
I bought the player as ive been waiting for Denon to hit a home run with a DVD player. Im still waiting... The player overall is good, the picture is good, and the sound is excellent, but it left me wanting more. I still prefer the Panasonic picture, but this is on par with the 3800. Of course the price is a big negative, but you do get SACD and DVD-Audio.
I think Denon should bill the player as a SACD/DVD-Audio player that also plays DVD's since the audio shines and the dvd is above average. Just my 2 cents. I also want DVI at this price point, but thats another issue.