Fedora versions

[Mark]

I have a general question about the different versions of Fedora:
What is the basic difference between the versions? I started off my servers with FC1, in the meantime FC3 is available.
FC2 never installed properly on my older machines, so I skipped that one.
How save is it to use the FC3 installer to upgrade an old FC1 system?
Or would I be better of just using up2date to update my FC1 RPMs from the FC1 channels?

What's the best practice to deal with these changing Fedora versions?

Thanks,

MARK