I wish I could give 4.5 stars, as this is one of the best bakeshops I've ever been into. Squirrel Hill is easily Pittsburgh's destination neighborhood for desserts and sweets.
They serve five varieties of cupcakes every day, and that menu repeats weekly. (Monday has the same things as last Monday.) There's great variety and experimentation here; everything from "vanilla" to "pancakes and bacon", and some whiskey-chocolate concoction that wasn't half bad.
They have, hands down, the best icing I've ever had on a cupcake.
On the minus side, the non-vegan cupcakes are often dry, and they only really have seating for two folks at a time, which is problematic when it's not warm outside here in the winter.
Go here. Try at least two different cupcakes. It's awesome.