I've been cooking with a Mirro 4-qt. pressure cooker for years - just like the one my mom had.  When I had trouble getting a replacement gasket that actually fit (the one that is supposed to fit is not wide enough) I decided to just upgrade my cooker.  I went for the Presto 6 quart stainless steel one - stainless was just a few $$ more than the aluminum - and I'm so glad I did.  Not only is is a heavier pot but it cleans up so easily and is so much better looking than the aluminum one.  I had to attach the handles when I got it which was very easy and the pot works perfectly.  It comes up to pressure much faster than my old Mirro and, even though the jiggler is different from my old pot, makes a very pleasant noise while cooking.  I love this pressure cooker and cannot recommend it highly enough.