Ok so something is definitely weird because it still does it regardless of how I'm holding the device. Tried covering various areas and couldn't replicate the exact timing of the behavior, but couldn't discern a pattern with it during normal usage.

EDIT: So the manual says that the ALS is to the left of the Nokia badge on the front...no way I'm covering that. Behavior is just like described here:

https://bugs.maemo.org/show_bug.cgi?id=2755

Anyone else with their device notice this?