Wallie, I am not disappointed or weirded out by the fact that the AMG cars have automatic transmissions. I think it is actually good because Mercedes has perfected the automatic (no longer a 0-60 difference with manual and automatic for MB) and it is a great transmission. I guess I would really like to see a manual transmission in more entertaining cars than the regular C Class. Having the 6-speed manual available in the new SLK350 is an amazing new step for Mercedes.
As for the Benz's you've driven, that's kind of ironic. My parents each have an 04 S500 4Matic (both of them non-sport package) and I have an 02 ML500 so I can easily relate to the Mercedes vehicles you've driven. The S500's are great vehicles but I feel like the car is very calm about its power, which is typical Mercedes style. The transmission is always very quick to keep rpm's down, but when you active the Sport Mode 2 (mode 2 being the most aggressive, mode 1 being less aggressive, and default of it "off" being the most comfortable ride), the big heavy beasts are surprisingly nimble handlers through the turns despite a bit of squishiness due to the standard gay 17" all-season tires.
As for the ML500, I think it is an underrated SUV. Granted the styling isn't for everyone, I think it has good strong points, even compared to the new SUV's available on the market. The vehicle costs $50K very nicely-equipped and it is a mid-sized SUV that does not compromise. It seats 5 adults comfortably, has ample trunk space, standard 4WD with Low-Range, and all the other features you expect from a luxury SUV nowadays. And to top it off, it has surprisingly good on-road dynamics. Acceleration is great and the 5.0L V8 sounds great all the way to redline (very loud and macho sound coming from the engine that the S500's just muffle down), and the suspension is great. It rides like a typical "truck" over the bumps, but it can take turns surprisingly fast with very predictable handling, and the vehicle overall is very nimble.
I think Mercedes really knows what they're doing with their cars and they seem to be only getting better and better.
Grunt, I agree with you. If there was no BMW, the Audi S4 is the way to go. I always thought the B5 S4 was an amazing car and this new B6 S4 is an even more amazing car.