It's worth poking around the sale, but before you buy, it's also worth noting the terms. Tickets purchased through this sale are not eligible for refunds and there is no advanced seat assignment option.
Additionally, Frontier has occasionally complicated baggage fees and they charge for full-size carry-on bags. Those fees can vary, but the carry-on charge is generally around $30-35 if you pay at least 24 hours before the flight. The fees increase if you purchase at the counter.
So, unless you're accustomed to hopping trains with a bindle, the cost of a trip with Frontier can add up. But if you're able to pack light, this is a deal worth jumping on. Save that extra money for something special that doesn't involve any weird relatives.