Doubt that anyone does use it seeing it is from 1962.. The specs arn't all that great Heathkit Virtual Museum | AA-151
There are plenty of 50s and 60s tube amps still in operation out there, so I wouldn't write off anything due to age... as long as it's been taken care of and serviced/restored when needed. I have a Heathkit AA-161, which is a mono amp. It's a decent little EL84 powered amp, but doesn't quite stack up against my Fisher 100, Fisher 400, or even my Voice of Music 1428. Mine is unrestored, so I really don't run it... but I might have a go at replacing the caps someday. Also keep in mind that since these were kits, build quality is going to vary from example to example. If you can find a nicely-built example that is restored, I can see it being an enjoyable amp to use. Here's a nice-looking example someone posted on YouTube:
