You can "downgrade" with patches too, although to be quite honest it can be
painful due to some strange behaviour (I'd call it a bug, but it might be
documented) with reverse-patching files that are created by a patch.
Essentially, you can do
cd /usr/src/linux /* latest 2.0.23 kernel */
patch -R -p1 < ../patch-2.0.23
/* now it should be 2.0.22, because patch 23 got "R"eversed */
patch -R -p1 < ../patch-2.0.22
...
Yes, it would be easier if I made patches from every version to every other
version, but it would be easier for YOU. Uncaring bastard that I am I whisper
"damn suckers" under my breath and cackle hysterically when I think of all
the clueless newbies destroying their source trees by a mispatch.
Mmmbwhahaahahahaaa..
Linus