One thing that users may notice in Fc5Test3, the gnome-power-management icon will show up for every user. I don't know the reasons behind this, but my opinion is that it is easier for users who do not want this to disable it than it is for users who might find this useful to find and enable it. You may also find that the click menu items to suspend or shutdown have been removed from the icon, as they are going to be moved to the System menu instead.
Another change that users might notice is that System -> Shutdown isn't available anymore. Seth Nickell wanted to experiment with replacing the Shutdown item with Suspend, given the idea that most the time you want your system to suspend rather than shut down. An example was given that your TV, although you press the power button, it actually does a suspend rather than a shutdown. As others have pointed out however, you usually don't apply software updates to your TV or take your TV with you as you roam about. Personally I think the experiment is a failure in that shutdown needs to remain an option, especially since it is the way to get to Reboot. The Linux Computer just isn't ready yet to not have the ability to easily shut down or reboot the system. I don't know of any official ways of gathering user input on this experiment, but probably voicing your opinion on fedora-test-list will be one (noisy) way of getting your opinion heard and taken into consideration. I'm hoping (and I'm hearing it will probably happen) that the shutdown menu comes back.
As far as infrastructure goes, this will be the first release using the new unified SRPMs layout that I have been working on. No longer will each arch have its own SRPM CD set. There will be one global source/ directory and within it there will be a SRPMS/ dir and an iso/ dir. The isos being made from the SRPMS/. The SRPMS/ directory will have repodata so that yum can be used to obtain srpms. Also I have removed the debug/ directory from the os directory where it used to live. Now the debug/ is on the same level as os and contains its own repodata and repoview content. I wanted to separate debug packages from core packages so that end users don't have to process the repo info for all the debug packages when they are using yum. So now those of you that need to debug stuff you can enable the debug repo and the srpm repo and be able to do these tasks in an easier way. This also makes it easier for mirrors to elect not to mirror debug or source content. This means we may have to munge the mirror list a bit. For this reason (and possibly others) the debug and source repos are pointed directly to download.fedora.redhat.com. I urge you to check with a local mirror to see if they are mirroring that content and if so change to use that mirror. It will lessen the load on d.f.r.c and hopefully provide packages to you in a faster manner.
Users who are going to try to upgrade will notice that just about every package will be upgraded. This is due to the multiple rebuilds we've done of every package gcc touches. This is to discover any problems with the upcoming gcc4.1 release, and to use some of the new security features of the gcc4.1 snapshot we're shipping with Test3. If you are using your own compiled software, please try recompiling it with the new gcc in Test3 and report any actual compiler problems.