One of the most annyoing things in Fedora Core 5 is that there is no default update system that informas you of available updates.
Sure, the nightly yum update can be chosen as well as the smart package manager, but a build-in default with a nice graphic applet would be much nicer.
The project to create such an applet is called yumapplet, the project homepage is here. As far as I know there are already some codelines written and we can expect a working applet in Fedora Core 6.
At the moment the more non-technical discussions are around the GUI, or better said, around how the applet will look like in the task bar: this page shows how much effort the people in these days put into the graphics to get a smooth and nice looking system.
However, one thing that I really miss in yum is a possibility to continue working even when all mirrors of a given repository are failing. For example, the ifolder people do a great job with providing their software in a yum repository for Fedora Core 5, but this directory is sometimes missing and therefore yum cannot work due to a failure reading in all repository information.
Since the XML metadata package format is now also used by the openSuse build server and more and more other projects the chance that there is one single repository that will fail during the start of yum grows and yum become more and more fragile. I filled a bug report to address this issue, please leave comments there if you agree or disagree with this point of view.