To the extent that EF is a good tool for finding fare availability in certain buckets (including those for discount premium tickets), it can certainly be used as a means to get lower-priced tickets -- but this functionality is really no different than what you could get from similar websites that don't charge the $5 per month, such as www.seatcounter.com.

The best functionality of EF (and the reason why I subscribe) is the ability, for many airlines, to see hidden buckets -- namely, upgrade and award classes -- that make it easy to see availability without making repeated calls to the airline.

Mike