Eh, how often are you going down to the bit representation of signed integers? Naturally I learned two's complement ages ago, but all of my bitwise manipulation seems to be on unsigned integers (and frankly I've only used bitwise operations at work once for implementing bloom filters. Normally I only get to do lower level stuff like that in side-projects). So internalizing two's complement has never seemed relevant.
> And a byte value of 128? What is that in hex?
0x80