I've spent two decades writing C and C++, but the last 8-9 years in really high-level languages (Ruby, Javascript, Python). From either end of the spectrum, I've never felt the need for such emphasis on fixed-sized numeric types. I've commonly needed access to fixed size numerics, like when sending texture formats to the GPU, defining struct layout in file formats and network protocols, but I have never once thought:…
For those who don't know, C's char, short, int and long data types aren't really "fixed size". The standard defines their order: sizeof(char) Now you may be thinking "sure the standard says they could be different, but they aren't really, a char is 8bit, a short is 16-bit an int is 32-bit a long is 64-bit". So here's a couple examples for you: many DSP platforms have a C compiler where char is 16-bit. Also Microsoft Visual c++ on windows on x86_64 compiles longs as 32-bit while GCC on Linux on x86_64 compiles longs as 64-bits.
>Notice how smooth the 32-bit to 64-bit transition went? (and yes, it was smooth.)
I know you said it was smooth, and maybe it was for some applications. But for many others, the 32-bit to 64-bit transition actually caused a lot of problems! Andrey Karpov has already done a great job of categorizing many of them, so I won't waste my time repeating him, but you can read his list here: http://www.viva64.com/en/a/0065/