Fiesta Farms is my local grocery store and, as a result, I always look forward to my weekly grocery shopping. The first couple times I visited Fiesta I was frustrated that they don't carry some products (e.g. crumpets) that the chain stores carry and that the layout is not very intuitive. However, I'm now used to these things and I actually like that Fiesta's layout is nonstandard - it reminds me that I'm not shopping at a chain.
I would say that Fiesta has a well curated selection of products. They don't have the ridiculous variety of brands that a place like Loblaws has. Rather, they pick the best brands and also carry some interesting things that you won't find in Loblaws. Their international section is quite good and, as Val G has noted, they have a focus on organic and alternative foods.
You won't find 100 types of granola bars at Fiesta like you could at Loblaws but you just might find 100 types of olive oil.
As a vegetarian that likes cooking from scratch I spend the majority of my time in the produce section. Fiesta has great fruits and vegetables and they have a sincere focus on local sourcing.
On top of all these tangible characteristics that I love about Fiesta there's also a certain less tangible quality that keeps me coming back. There's something about supporting a local business and seeing the same customers and staff each week that I like. It's sort of a community feeling.
Pro Tips:
1. Fiesta has a lot of interesting products and I try to impulse buy something I've never tried before each week. Some things I've discovered this way are: Sunflower Kitchen hummus, Macedonian feta from the deli counter, and Abuelita Mexican hot chocolate.
2. Talk to the manager of the produce department, especially during the growing season. He's extremely knowledgeable about what fruits and vegetables are best that week. I've never gone wrong by listening to his recommendation.