I use EF very often for looking up flights and finding options which I wouldn't have ordinarily considered. One time I saved my company HK$30K by finding a JL flight to North America that was cheaper than a corresponding CX J fare.

Nice because you can search by alliance and/or by airline.

Also seat maps are good. Nice to be able to tell your TA which seat number you want instead of something vague like "aisle seat near XYZ area".

I have the Premium version and well worth the $10/month for anybody who travels somewhat often. For the frequent traveller, it's a must.