I have only ever used debian/apt based distros but I have been trying Fedora 4 for about 3 days and I just can't get my head round yum at all.
Firstly, with the default repos set up i got 3 different results when checking for updates in kyum, yum extender and yum command line.
yum check-update in console listed no updates.
yum extender listed 5 updates.
kyum listed 12 updates.
I checked and double checked that they were all using the same repos and after trying each one 4 times I got the same results.
I've tried using different repos and still get different results in each when checking updates.
I've also tried completely removing yum altogether and reinstalled it and still the same results.

Secondly, I don't really understand all the third party repos and what they actually provide.
Are they just the same packages but repackaged by someone else?
I've been googling all day and have just ended up even more confused. Some pages say livna is not compatible with the default repos yet the livna website says it must be used with fedora extras which was set up as default.
I've read countless times that 3rd party repos shouldn't be mixed but I can't find anything which tells me exactly which ones work with which.
Can anyone point me in the direction of a definitive knowledge base?

Perhaps some mirrors are not as updated as others and it chooses mirrors at random and so sometimes it finds a mirror with lots of updates. I think if you run it multiple times you should get all the updates.

Historically, there have been two groups of third-party mirrors. There is the Fedora Extras (formerly fedora.us) and the livna repositories; and then there are the dag/freshrpms/dries/newrpms/PlanetCCRMA (RPMforge) repositories. Each group's packages are compatible others from that group and the Fedora Core base packages, but when you mix packages from the two groups (especially Livna with the second group) you get a lot of incompatibility problems.

The first group has the advantage that they work closely with the Fedora Project people (especially now that Fedora Extras is part of the Fedora Project and is enabled by default); but they don't have that many packages (in particular, Livna only carries packages that can't be hosted on RedHat servers for some reason). On the other hand, the second group has far more packages, but are made by individial people who may not be so closely associated with the Fedora Project, so some question their quality.

do a yum install yumex from the SU command line and make yum much easier to live with.
restart kde and open /start applications/System Tools/yumex and you will have a beautiful GUI to work with.

Jim

The OP's already used yumex. It's not the problem.

Thankyou, that's cleared things up a little regarding the repos. I'll just experiment with both groups to see which seems better for me.

Regarding the yumex/kyum/commandline problem - I tried checking updates again today and this time yumex listed 1 update and both command line (yum check-update) and kyum listed 5 updates.
I updated via the command line and now all 3 are showing no more updates so I'll see what happens next...