I just upgraded my office workstation from Fedora 10 to Fedora 11 via preupgrade, one of the two officially supported ways of doing it. It took four hours. Of course, my machine was effectively down for those four hours, as it was off the network and unusable.

(While my office machine has a lot of RPMs installed (2742 after the upgrade), it is not a slow machine, so I suspect that this is not an unusual thing.)

I know, Fedora doesn't officially like upgrades; they want you to reinstall from scratch every time. Newflash to Fedora: this is not viable for real people using your distribution for real work.

For me the major problem is that four hours of downtime. I don't care if the upgrade takes four hours, but I do care a lot if I can't use my machine during that time, ideally with some reasonable facsimile of my regular environment. Thus there's two good options that I can see; either really supporting yum-based upgrades or creating a 'live cd' style upgrade environment. I would prefer the former, but the latter is probably easier (although doing a good job is hard, since you want to pull as many settings as possible from the user's regular system).

(It's possible that something horribly slow that shouldn't be happening is being done as part of the upgrade process, as I am pretty sure that installing from scratch would take substantially less time than four hours, and there's only so much that can be blamed on filesystem fragmentation. Alternately, there is or was something quietly but badly broken on my Fedora 10 system that caused the upgrade to be very, very slow.)

(I would like to say that a basic live cd upgrade environment should be easy to put together for Fedora, but I can't actually remember if the Fedora Live CD stays 'live' if you opt to install the system, the way that the Ubuntu Live CD does. If it does, an equivalent version for upgrades ought to be easy since both installs and upgrades use Anaconda.)