We don't have them out west, but my in-laws in TN shop there a lot. They are immensely popular there. We've popped in a couple times to check it out. My impression was good quality produce, frozen stuff and shelf products at very good prices. The things I really loved were (1) the fact they charge for grocery bags, which means most people bring their own, (2) having shoppers bag their own groceries, which I do better than most employees anyway, and (3) requiring shoppers to deposit a quarter to get a shopping cart, which you get back when you return the cart. It means the store doesn't have to send employees out to collect carts, and your car doesn't get banged up by inconsiderate shoppers who can't be bothered to return their carts.
If you have Aldi markets where you live, have you tried them? What has your experience been?