The Ballard Farmer's Market has as much variety as any farmer's market in the city. In addition to a couple dozen produce vendors, ranging from specialists that just sell berries or stone fruit to more general farm stands, there are prepared foods ranging from Veraci's pizza to donuts, and several stands selling other farm products like flowers, honey, cheese or meat. There are even some craft stands with jewelry and other art. The many restaurants along the street are also mostly open, so there are plenty of options for lunch.
The produce prices vary wildly. Often the first vendor to have a particular item will gouge, and the stands nearest either entrance tend to have higher prices to profit from the impatient shopper. Not all the stands are organic; most of the lower price stands are selling the same produce you'd get at a decent supermarket. Spending a little time to scope the place out before buying anything will usually mean good prices on fantastic produce.
Scoping out the place could be a problem, though, because of the location. The street the market is held on is simply not wide enough for the number of people that attend. The western side of the street is jammed during the summer, with cyclists and people pushing huge strollers adding to the bedlam. The eastern side is significantly wider, but it's also peppered with street musicians and can also be quite crowded.
Parking is also an issue; you either have to circle until you catch someone leaving, or park well away from the main drag of Ballard.
If the market was relocated to a much larger space, I think it would easily be the best in the city. As it stands, it has too much of a hectic street fair atmosphere for my tastes. The University Farmer's Market has similar selection and more manageable crowds, while many of the smaller neighborhood markets offer a decent selection of produce with slower-paced, more intimate feeling.