We have always thought of US Cellular as worth a premium price, after all, they're a real carrier. However, when there's a chance to do it cheaper, we take it. If you live in US Cellular territory you can use Google Project Fi and enjoy the benefits of US Cellular for a much better price. However, the chances of using their network is low if Sprint and T-Mobile are nearby. We can't predict which network gets priority, but we can be fairly certain that where US Cellular is your best, or only, choice, Google Fi will find it...which is a good thing.
Google Fi can also seek out a Wi-Fi network, so your chances of using US Cellular are potentially even less, unless a nearby "Off" switch removes that Wi-Fi from the equation.