Thanks the the immediacy of the Interwebs, I can begin answering all your obsessive questions about the SK3. Let's begin by noting that thus far I've been a smartphone Luddite. The vagaries of spam, my various email accounts, and the desire not to lose my wife because my phone is vying for my undivided attention all worked together to cause me to use and carry only standard phones with some sync capability.
Therefore, for me to use and enjoy the SK3 was a big step for me and attests to its value, if not its utility. You all asked me if I preferred the MDA. In terms of being a "real" smartphone, the MDA is far superior. It has a full complement of applications that the Sidekick series technically lacks. However, the SK3 isn't a geeky device. It's a general purpose device, designed for the non-geek. If you go into the SK3 expecting amazing performance, you're going to be disappointed. At T-Mobile's price-point, they're not going to be able to put much more than the absolute necessities into this thing, and those necessities are more than sufficient.
As for the minor annoyances I experienced, I'd like to chalk them up to a pre-release unit. I can't confirm this, but we'll see when these things hit the street how they work.