Comment by tengwar2

Depends on whether you have a suitable problem, and the problem domains have shrunk greatly over the last 40 years. I've used it for bit-twiddling in real-time data acquisition; for implementing a GUI (on OS/2 1.0, which didn't come with one) and for acquiring a handy character set for the same from DOS; for accessing some obscure features of the PC architecture (thanks, Thom Hogan); for trying unsuccessfully to access paged screen memory with an RSX on the Z80 based Amstrad; and for successfully implementing an RSX to quash high-bit characters from the keyboard on the same to deal with an editor which had an array of only 128 characters for deciding what to do with input.

All of them apart from the screen memory thing were fun, but the only one which could be useful these days is the bit-twiddling. All the rest have been made obsolete by improved operating systems, so that the domain of useful assembler programs shrinks ever further. OTOH, debugging them is vastly easier than in the old days where all you got was random lines drawn across your screen as the system crashed, and you couldn't even single-step because you had to bank-switch out.