Update:
This weekend I picked up a pair of el cheapo pedals w/ toe clips and straps. I've ridden them around 25 miles so far I guess. I am adding foot retention to the list of things I should have been doing 10 years ago. It's not exactly like it made me that much faster, although I did average around 2 mph faster on my commute this morning. I'm pretty sure the "planing" that I had been experiencing intermittently was just when I happened to be seated correctly on the bike and pedaling smoothly at a good cadence. The toe clips and straps force me to pedal smoothly, and also make my fit adjustments easier to feel/adjust. My entire ride this morning was of that "planing" sensation I was feeling before.
I have a leg injury I've discussed in other forums that leaves me with a significant strength/flexibility imbalance and the clips/straps also help immensely with that, so much so that I'll keep the retention regardless of any performance gains or go-fast feelings.