Those do look pretty cool, but still wouldn't be a substitute for a head check before changing lanes..... or would they??????
I say that depends on how fast things are changing ahead of you. When things happen fast and I have to make a quick decision to live with or die from, what's registered in my brain from the last mirror scans is the information base for the decision.
There have been more than a handful of situations where the split-second required to make a head check would put me too much out of touch with what's going on ahead. I use convex mirrors much in the same way as a radar detector. It's another tool that provides more information about what's going on. They are certainly not a substitute for opportunity or stand-alone certainty.