I also think that the fact the chip is smd is a problem for hobbyists.. One feature everyone loves is the 'roll your own' aspect of Arduino.. Through hole is what hobbyists generally want.. And the chips are cheap. I haven't gotten and done any ATTiny chips, but they are supposedly usable for Arduino projects.. And I have seen those suckers for REALLY cheap, even in single units. I'm going to pick up a 40pin AVR, ala Bobduino, as I want more I/o than the 328. It's still through hole, so it's not too intimidating. A board with big resources is great.. But like the mega, I wonder about the impact of using a format that is proprietary in terms of pin layout, the headers are the biggest problem with the design.. They plain suck, especially since they neither mate to a breadboard OR accept wire jumpers reasonably. BAD design... Why keep on making the same mistake going forward? Make a cheap adapter for older shields, publish the new pin layout, done.
Better yet, if you want, leave the dang headers, but also put pins on the other side, so the Arduino board can be directly plugged into a breadboard in the same manner as an Adafruit BoArduino.. Imagine how much easier your prototyping would be just plugging the bugger into a breadboard without a billion jumpers that are unreliable at best due to poor quality headers!