As seen in passing on Paul
Frields's weblog: it appears that the deltarpm feature is not going to
make it into the imminent Fedora 11 release after all.
There is apparently work to be done on Fedora's internal update systems which will not
be completed in time. That's an unfortunate development, but, at least,
Rawhide users are able to use this feature to reduce the pain of keeping up
with the update stream.