Trader Joe's has a solid reputation and loyal customers, myself included. It's a quirky place, but in a good way. It seems like their staff goes out of their way to be extremely friendly and accommodating. Such a breath of fresh air compared to other grocery stores.
TJ's offers great quality foods at very reasonable prices, especially their own Trader Joe's branded items. A lot of their stuff is organic and geared toward the food conscious grocer.
They have a nice selection of boxed, packaged and frozen items, but the produce section is lacking. They also don't have a live deli or meat & seafood counter. This is my only beef with them. They do offer a limited selection of fresh packaged meats and Cryovaced deli choices though.
The wine and cheese selection and value are amazing (Charles Shaw). They also have some really good TJ brand beer.
I do recommend subscribing to the TJ Newsletter. It's an old fashioned newsletter with comics that announce TJ happenings, sales, tidbits and other helpful info on the store.