According to the info, the D7100 upgrade does include a fix for a possible metering problem with E type lenses and Live View, which I've not encountered, but figure I might at some point, and I've thought intermittently about getting one of the 10-20DX lenses for traveling, so I did the upgrade with no issues. The only AF lens I have that's not a Nikon is a moldy Tamron screw drive one, which I haven't tried, so no compatibility issues here.
They do warn that this upgrade will reset various settings, which I don't recall seeing in previous ones. I didn't try it after updating to see what settings actually were changed, but had no visible issue saving and restoring. Everything seems to be as it was before.