Why does it take so long for new (gimp, kernels, openoffice) packages to reach the stable repo ?

[Linuxguy123]

I'm waiting for gimp2.6, kernel 2.6.27 and open-office 3.0.  If I am not
mistaken, there are a couple evolution releases that haven't been
accepted either.

All of these packages have been released for general distribution
outside of the Fedora community.   Why does it take so long for them to
be accepted into the Fedora stable repo ?   

Are they unstable and do they need bugfixes or what ?