Here is about the best response I have seen to-date regarding aluminum pots;
I have investigated the use of aluminum in every brewing text I could lay hands on, including some very old ones. Regarding aluminum kettles, I came up dry. It seems the metal has never been considered for brew kettles until home brewers came along. I suspect the reasons for this are purely practical. Kettles are the hardest of all brewery vessels to clean, and strong chemical cleaners corrode aluminum. Caustic soda literally eats it up. It is soft enough that hand scrubbing with wire brushes will scratch it badly, which in turn will make the surface harder to clean the next time around. It is no wonder that commercial brewers apparently never considered using it for brewhouse vessels.
It came from Brewing Techniques web-site http://www.brewingtechniques.com/library/backissues/issue1.4/miller.html
And he sums it up best in the last paragragh;
Meanwhile, my advice to anybody putting together a home brewing setup remains: Copper and stainless are the best materials for a brew kettle. Enamelware works, though it is harder to clean than copper or stainless; it is even cheaper than aluminum. I see no reason to buy an aluminum kettle for home brewing.
He says in the article that he can see no real good reason not to use aluminum, he even talks about iron as a brew kettle. Even when John Palmer talks about aluminum, he doesn't just come out and say use aluminum, it's simply listed as a choice.
I'm still going to go with my original choice, stainless. It should last longer, and I won't have to worry about "being careful" when I clean it with-in reason. I have scorched mine, and it cleaned up quickly with a green scrub pad (gently of course, just enough to lift it) and then I was done.
And this takes the cake so to speak;
DM: First of all, I would not pay $100 for an aluminum kettle. For that kind of money, I could get a stainless steel Sankey keg and have it modified to make a first-class kettle, with none of the doubts or disadvantages aluminum carries.
$100 is high for an aluminum stock pot, but I have seen them for around $50-$60 range for a 40 qt. and for that kind of money, I can get a half barrel sankey keg, cut the top out, put a weldless bulkhead in it and now I have a 15gal brew kettle.
As a side note, I bought a 34qt turkey fryer from sam's club for $78 with burner and stainless base and pot that works very nicely, it's not the best pot I have ever seen, but it's holding it's own.
Aluminum is an option, but it's not the best one for the money, it has more than it's fair share of drawbacks. If you do a little shopping around you can find a better option for just a little bit more money. If it works for you, great!, but I wouold not go in search of an aluminum pot to make up my equipment with.