After adding the 'extras' repository during a network install of F7t4, going into the package customization screen you will notice that most of the default package groups are not checked (i.e. no base-x, no gnome-desktop, etc.) Basically, it seems that if you add Extras, you need to go into the package customization screen and re-enable all the stuff that's not listed in extras' comps file. Everything seems to install normally if you don't go into the package customization screen, though.
I don't think this is a comps bug, but an anaconda bug. Anaconda (pirut) should be showing the merger of the two (or more) comps files.
This is messy, but not a default-install type thing, so it's not a release blocker. It is kind of nasty, though - drops a whole bunch of packages if you enable extra repos. Will there be any movement on this for F7?
This actually looks like it's even just a display problem; the packages are getting installed even though the groups aren't showing up as selected. And things look right if there aren't overlapping group names (eg, my sparkle motion repo ;-) Still going to try to get to the bottom of it as it's bound to cause confusion and problems...
Fixed.