I was using one before I got into the phased verticals and had good results with it. In a sense, that's what the EWE is - two phased verticals in an endfire arrangement using the top horizontal wire connecting the two verticals as your phase line. The only downside is the antenna is very dependent on grounding so if your soil conditions are really, really bad then it might not give you as good of performance.
How far apart are your trees? I don't know of any tree distance/Freq. formula, but IIRC the rule of thumb is twice the distance per vertical height. I had two pines that were 14' apart so I set my verticals up 7' high and had good results. You do have to use a 3:1 transformer to knock it down to 50 ohms.