The one abstraction you would have to keep in mind with assembler (writing more than reading tho) is the cache hierarchy. The days of equal cost to read/write any memory location are ancient. Even in the old 8 bit days some memory was faster to access than others (e.g. 6502 zero page).

The flags are another abstraction that might not mean what it says. The 6502 N flag and BPL/BMI instructions really just test bit 7 and aren't concerned with whether the value is really negative/positive.