Should you try them? Yes! at least ask to try one.
Where to find them: Farmer's Markets
Where I work, we sell and sample a lot of fruit. Our most popular sample item is the gooseberry. Gooseberries are "sweet-tart berries." As a fruit they are sort of like a mix of a grape and a kiwi; they have the size, texture, and skin of a grape, but the small negligible seeds, hair, and tang of the kiwi. The tastes are somewhere in between.
They are without a doubt, an acquired taste. Some people find them too sour. Like most fruits, gooseberries get sweeter as they ripen, but the line between sweet and ripe to sweet and alcoholic is pretty slim. While there are a lot of different gooseberry varieties, the most common difference, from what I've seen, is green versus red.

Red: Usually higher sugar and higher acidity than green, darkens in its color as it ripens. Best for eating, jams, or baking. My favorite summer snack food.

Green: These go from a bright, yellow-green to a more translucent and darker skin as it ripens. A much milder berry than the red ones. The green gooseberries are the most commonly found variety. Great for things like gooseberry fool.
So, go find them! Gooseberries are only in season for a little bit more (sorry, this is late).