Maybe it changed more recently, but in the first couple years after acquisition they (WM and Jet) had very different approaches to things like search and there was a lot of internal conflict over whose was better. I think they pretty much just kept things separate as a result, so probably not a lot of long-term tech value attained by WM.
I wish you would put the "Read a message" button above the content so it doesn't jump around vertically each time I click it.