Let's get the discussion rolling! We installed the 5910 tonight. As it is not yet calibrated to our display there is not much fair to say about the visuals. It is replacing a 5900 in our setup.
A few observations about the cosmetics, in comparison with the 5900. The 5910 looks big and square compared to the more sleek lines of the 5900. All the logos are white printings behind a glass panel. Much less attractive than the silkscreened on aluminum of the 5900. There are brightly blue lit logos for DVD-Audio/Video and SACD. These dim when the unit panel is dimmed. What does not dim, however, is the big circular power button. And for some unfathomable reason, it is GREEN when the unit is on! That's more than a matter of tasteit is flatly annoying. It displays a large red circle when on standby.
As for the rear panel, the RCA connections are the classiest I have ever seen. However, unlike the predecessor, none of them are color coded, oddly. They are very nicely spaced, which helps with connections if you are working in tight corners. The DVI jack is a cheap looking silver one that looks very out of place. Power cord attached snugly.
The remote is nothing special and probably no one would want to use it. It does have full backlighting you may switch on. It also has output format switching for DVI/HDMI which is very helpful for our purposes, and saves a lot of running up to the unit (wow, did I get flamed when I complained about that aspect of the 5900). Otherwise, clumsy with tiny labels.
Navigation is not the fastest but significantly faster than the 5900, at least with the firmware we were running. We did do some SACD listening, via the analog outputs, multichannel. Played a few tracks off Peter Gabriel Up which sound like mud on lesser players, which I have listened to many times for comparisons. Maybe it was just my imagination, but to me, it sounded noticeably more open and detailed than the 5900. And then I did not feel so bad.
As an aside, while this thing is pricey, I counted 27 more expensive DVD players in a current buyers guide from Sound and Vision. Helps to put it in perspective.