starting fc18 presto-plugin has disappeared
I would like to get yum out of this mode.
Can't find a conf switch or trick to do that in man or google.
Is this another choice removed from "Linux,the world of choice"?
Or can I get a hint from here?

Try install presto yum plugin.

yum install yum-presto

[dw-agagne ~]# yum info yum-pesto
Loaded plugins: langpacks, presto, refresh-packagekit
Error: No matching Packages to list
[root@dw-agagne ~]# yum info yum-presto
Loaded plugins: langpacks, presto, refresh-packagekit
Installed Packages
Name        : yum-presto
Arch        : noarch
Version     : 0.9.0
Release     : 1.fc18
Size        : 66 k
Repo        : installed
From repo   : fedora
Summary     : Presto plugin for yum
URL         : http://www.lesbg.com/jdieter/presto/
License     : GPLv2+
Description : Yum-presto is a plugin for yum that looks for deltarpms rather than rpms
            : whenever they are available. This has the potential of saving a lot of
            : bandwidth when downloading updates.
            :
            : A Deltarpm is the difference between two rpms. If you already have foo-1.0
            : installed and foo-1.1 is available, yum-presto will download the deltarpm
            : for foo-1.0 => 1.1 rather than the full foo-1.1 rpm, and then build the full
            : foo-1.1 package from your installed foo-1.0 and the downloaded deltarpm.

Alan