Like you said, its better but not that much than 5.1, IMHO we have too many surround formats going on currently and the addition of HD just made it that much worse. Heck I have to upgrade my receiver just to listed to hd surround formats...
Which brings up an interesting point. The manufacturers count on the fact that the product life is much longer than the functional life, especially for receivers.
We have already been through 4 or 5 generations of Blu-Ray and the product is less than 4 years old. Each generation has added new and "essential" features.
If you look at receivers, you will see yearly model updates with new features, all of them "essential"
So, when is the proper time to upgrade? If you buy new equipmment every year, you lose about 2/3 of your investment on resale. If you wait, you start to get envious of all the cool stuff you are missing.
The trick seems to be sorting out what is really new from the gimmicks. I tend to wait until a year or two after something revolutionary happens as there is usually a series of improvements to the original concept. For example, when Dolby Digital came out, receivers added DTS about a year later. Then, quality of the produced sound remained the same for over 10 years until the HD formats emerged.
I will probably get roasted for this, but Audessey falls into the gimmick catagory. It may take a little longer, but you can set up a system that sounds as good without it. All Audessey does is take the work out of setup, and doesn't improve the inherent quality of the receiver.
You could argue connectivity either way. It is a convenience to have one stop switching, but toslink for digital and HDMI for the HD formats was an essential upgrade.
So, I have had three receivers since 1989; a dolby pro logic surround one, a dolby digital/dts one, and now a HD format capable one. I probably won't upgrade here, unless I decide that the DD/DTS receiver in the bedroom is inadequate. To be honest, I'm running out of switching there.
And in the end, emotion is what makes the decision. Man is a rationalizing animal and will find the excuse to justify what one really wants.