When installing fedora from a CD there shouldn't be a problem in the time it needs to retrieve repo metadata files, but when the repo is not in a cd but online, in a http server it can be slow. I notice when installing fedora, there is a freeze while repo metadata files are being downloaded from the internet, perhaps the freeze could be replaced by a message saying what is doing and how much time will take.
The progress dialog boxes take the focus when they are running. The experience you are describing is deliberate. While repo metadata is being downloaded, we do not want you to do anything else in the installer (in fact, there's not much more to do except select packages, which is what the repodata is needed for). While it may seem unfriendly, it does ensure that the install steps are followed in order by the user.