tamiflu and xofluza are weaker than a lot of people assume. might shave off a day of symptoms at best. and like you said, you have to start it asap. most people assume the first day or so of the flu might just be a bad cold. for the cost of urgent care and whatever your rx copay is, i don't think it's worth the hassle. pretty much all you can really do is a ton of sleep, fluid, electrolytes, and ibuprofen and tylenol

but if you're intent on getting an antiviral if you catch the flu, one way to differentiate the flu is that it usually hits like a train out of nowhere compared to most common colds being more gradual