Today when I checked my network settings I saw that there in addition to the connection "Auto eth0" was the connection "Automatic Ethernet" (and I haven't added it myself nor done any changes to the network configuration). The only difference is that the latter has no assigned MAC address. Is this a sign of some new change to the network manager? Or what is it?
The answer to this would appear to be "yes".
The default name patterns for network adapters in Network Manager have been changed. I believe that upgraded installations will keep their existing adapter names.
Citation (idea marked as being in development March 2011) :
GNOME master bug (marked as fixed)