Great short intro! One other useful thing I'd add is that you don't have to have the register window open to see the contents of registers --- they can also be printed like other variables while you are in 'layout asm'. Or you can use 'layout split' which shows both source and assembly.
For example, "p/t $rax" will print the contents of %rax. Printing the floating point registers can be a little awkward, since they are written as a long union. But "p/f $xmm0.v2_double" will show just the two doubles, etc.
For example, "p/t $rax" will print the contents of %rax. Printing the floating point registers can be a little awkward, since they are written as a long union. But "p/f $xmm0.v2_double" will show just the two doubles, etc.