Thanks for all the advice guys.
I went into the shop thinking that I would do either the Speedplays or the DA pedals and wound up with Look Keo 2 Max pedals.
The rationale was this:
I am getting a proper bike fit done once I get some time on the bike in a trainer and maybe on the roads (if it ever gets nice enough). Once I "break in" my body to my bike, I will go in for a full Trek fitting. This fitting should dial me in perfectly in terms of adjustments including leg and foot positioning, which will presumably help out my knee.
My LBS convinced me that if I was doing that, I might want to consider a pedal that starts out with some float (the Keo 2 Max provides 4.5 degrees with the included cleats) but gives me the option of locking it into 0 degree float or 9 degree float with different cleats. I understand that the Speedplay Zeros would allow for that and more but my LBS didn't carry them and my dealer and wear over time would require a replacement of the pedal vs the cleat. Plus, I'm used to clipping and unclipping from Shimanos so the Looks were very similar.
He also convinced me that as a newish rider, it would be hard to justify the extra costs to get into a DA pedal as I probably wouldn't even notice the difference in weight.
In any case, I'm pretty happy with my setup thus far ... now to save for some wheels