ALDI is good for when you've got a lot of empty space in your pantry/freezer, but no at lot of cash in your wallet.
You would be amazed at the amount of stuff you can get for $20. I purchase mostly dry goods here, like pastas or cereal. The produce and fridge items look good but I'm freaked out by a $3 block of cheese.
I dont think you could do all of your grocery shopping here, but you can save a lot of money by supplementing your Giant Eagle trips to Aldi.
The frozen pizzas are good for a late night post pub snack.
Oh, and they dont bag your groceries for you and you need to bring your own bags, and its .25 to use a cart. Just be warned!