I expect that [AVRs] are very robust indeed. I would not expect MCUs from Microchip, TI, Maxim, NXP, ST Micro, etc. to differ significantly in that regard.
That would match my expectations as well. Semiconductor processes are pretty uniform, and you don't get to be the size of Atmel by selling chips that are not "Robust" (where "robust" means that they don't fail without encountering circumstances where you'd expect them to fail.)
There's a whole science to "reliability engineering." Spontaneous chip failures are not a likely cause of failures.
(Also, you can't be an Atmel (or a chip manufacturer at all) by selling chips just to hobbyists. Just because you can't find a list of products that use AVRs doesn't mean that there aren't any.)
[Atmel] Microcontroller segment net revenues increased 95% to $892 million for the year ended December 31, 2010 from $458 million for the year ended December 31, 2009. The increase in net revenues was primarily related to increased volume shipments from customers for both AVR and ARM-based 8-bit and 32-bit microcontrollers. Microcontroller net revenues represented 54%, 38% and 33% of total net revenues for the years ended December 31, 2010, 2009 and 2008, respectively.