I use a 60 qt AL stock pot with nice thick walls for my electric fired kettle. It's worked well for almost a decade now. The main disadvantages of AL in my case is that AL conducts heat better than SST and that means that my system loses a touch more heat. That means I have to turn up my electric controller a bit more...whoopee.
I don't scrub the kettle too hard. My main goal is remove all trub. However, I will alert you that the internal surface does build a 'varnish' layer from the wort. You can't see it until you give the kettle a hot PBW soak. A soak every few years seems to be frequent enough.