The Epcot World Showcase is always high on my disney to-do list. The shopping is pretty wonderful, not to mention the food, but the cultural value behind it is immeasurable.
Last year my brother and I took advantage of France and Italy to practice our French and Italian, respectively. We walked into the shops and just started up a conversation with the cast members behind the counters. I did horribly in Italy, but the cast members and I had a great time trying to communicate in their native tongue. The really enjoyed the effort I was making. As for the French, they were impressed by my brother's pronunciation, and were actually giving him hints and tips on the language.
Oh and the pictures. Maybe you don't find anything you consider worth buying, but there is a great chance to get pictures of your party shopping though some authentic looking markets. Mexico, China, Morocco, Japan, are just some that look as if you are in the country of origin, and while your party is perusing the items on display, it's a great chance to get some candid shots for the memories.
Also crazy/fancy hats! The World Showcase shops are a great place to find hats from each country, and you don't have to buy them. Just grab a few, take a funny picture and move on.
Last trip my other brother insisted on it.
As for things that are a must to buy for me, it all depends on what I'm looking for or if anything catches my eye. Usually it's the food and candy that does it for me. Though I'm yearly disappointed that Canada does not carry Maynard Winegums (gummie candy that does not contain any wine lol).
Just give it a chance, take a look, if you get board, you can always take one of the boats across the lagoon back to future world instead of walking the rest of the way back.