I see the Varia as an electronic mirror, monitoring the rear between mirror glances or distractions; complementary, rather than a mirror substitute. The Varia also detects vehicles as soon as they are *detectable*, which a mirror does also, but only if the visibility is good and the rider is also looking at the mirror *all the time*.
The intelligent light response also strikes me as useful, and appears to take approach angle into account. Another plus is the discrimination of multiple vehicles.
I would like one. Just $.