What are the advantages and disadvantages of courier services?

The main advantage of air freight is its efficiency. You can have packages delivered overnight, even on the same day if you send it over before the daily cutoff. Large logistics companies like FedEx and UPS offer this service by default, but local outfits like Ship2Anywhere (here in Australia) also accommodate the same through affiliate carriers. The main disadvantage of the service is in the cost, but it's still worth the investment if you're sending over valuables or you're rushing to meet a deadline.