Unclemat, interesting observations.
I've definitely found after some comparison listening I prefer letting Audyssey calibrate the distances/levels, then turning it off and letting the natural sound come through. Like you, while playing with it, I initially thought I preferred Audyssey, but after some fairly extensive comparisons, now feel it was overemphasizing things a bit for *my* taste (others may vary, and so may rooms of course). I have a pretty good feeling I'd feel the same about other receivers, whether an MCACC based Pioneer or newer Audyssey based Denon, but of course it's impossible to say 100% without listening to them.
That Denon does look like a killer unit - I was considering it, but decided against for three main reasons:
1.) Availability; I needed something ASAP and it looked like it would be at least a few weeks before it became available enough for me to do that.
2.) A Definitive Technologies tech I spoke to highly recommended Marantz for my specific speakers.
3.) I actually felt better about buying the SR7005 and having it be the top receiver for a while from Marantz than buying the 4311 only to have the "better" A100 version come out shortly thereafter; I know this one's purely psychological, but it did bug me and I think would have given me a bit of buyer's remorse (silly I know).
The main advantages I see for the Denon are the 140 w per channel (which I don't seem to need for my setup as this goes plenty loud for my small room) and the newer MultEQ32 vs. the XT on the Marantz (which may or may not make much of a difference per each individual room setup). Besides that, how much useful stuff does the Denon offer the Marantz lacks? IMO, the Marantz has a very nice/very modern feature set, but is one step behind the Pioneers/Denons in terms of frills.
Also, the more I listen, the more I'm liking what I'm hearing. Since owning the Marantz, I've done 3 Audyssey calibrations (one quickie; two complete, mainly after changing speaker positioning slightly, etc.), and now I can safely say it's been a few days since I've adjusted audio much at all. I don't know if it's break-in or just me getting used to the sound, but I'm finding I'm liking it more and more.
Enjoy your Denon, and I look forward to further observations. Is the Denon as warm as the Marantz? Are you auditioning them both to decide which to keep, or in a position where you get to play with different equipment regularly?