Yep. I went back and forth about the same decision in my 06 F150.
My thoughts were that, while a limited slip is nice, I really want to have all the traction I can when I need it. I had an aussie locker in the front of my last Sport Trac (front and rear actually) and the front locker made snow driving interesting in 4x4. It wasn't out of control, but it definitely wasn't ideal. In other words, I wouldn't go that route again on a daily driver.
While I haven't driven with a limited slip up front, I suspect snow driving would still be "interesting" with it, and when I really needed the traction it wouldn't be there.
There is also the tighter handling/steering in 4x4 with a locker/limited slip up front. I just wanted it to turn easily and not be stressing the CV joints and such when it isn't needed.
So I ended up with an E-locker up front. I cut out a hole in each side of the cigarette lighter panel and wired up my own switch. *disregard the lower panel, it was an experiment*
Anyway, so far the e-locker works great, I'm very happy with it. I haven't had a chance to put it to real good use yet, but have tested it in a few different areas and it works as it should. Having a rear detroit locker already, I really haven't had a reason to "need" the front locker yet.