I've shot pretty much exclusively aluminum and steel cased ammo for years. Not that I discriminate against brass, but I buy the cheapest thing available. I daresay that I have never fired a single brass round of 7.62x39. My handgun ammo for centerfire calibers is probably 75% - 80% aluminum. Sometimes the brass case is cheaper, or the same price, so I'll buy it, but that's the exception, not the rule. I actually PREFER aluminum cased .45 ACP because it loads into my moon clips more easily than brass.
I'm a pretty heavy shooter. I don't keep count, because I'd get depressed, but I would not be surprised to learn that I put 10,000 rounds a year downrange. I keep my guns in excellent condition. Most of my guns were not purchased new, and many are older than I am.
I have never had any of these problems. Cases don't get stuck in my chambers. Heads don't separate. Accuracy doesn't suffer. Gravity doesn't reverse itself.
(Actually, there is one notable exception to the above. When I shoot Super X 12 gauge shells, which are steel base, in my Izmash single-shot, they tend to stick. I have to "bump" the action 2-3 times to get them out. So there's that.)
Now, on the whole "dirtier" front, I do believe that cheap ammo is dirtier than premium ammo. What I save in $$$, I pay for in more time spent cleaning. Which is an exchange I am perfectly willing to make!