There has not been any decision whether the pure64/gcc-3.3 archive will
be dropped in favor the the amd64/gcc-3.4 archive. There are some 300
packages more available in the pure64/gcc-3.3 archive than in the
amd64/gcc-3.4 amd64/gcc-3.4 at the moment (~8300 vs. ~8000 packages).
I think that the amd64/gcc-3.4 archive will catch up in the next two
weeks so that nearly the same number of packages will be available
in both archives. However, the amd64/gcc-3.4 archive will still need a
few extra gcc-3.4 related fixes compared to the official sid/sarge
distribution. These are mostly minor one-line C/C++ standards compliance
fixes, but patches to the official packages will be necessary
nevertheless for these issues.
As for stability, I am using the packages from the amd64/gcc-3.4 archive
myself on three machines (on my main desktop and on two servers) since a
few weeks without any problems. From my own experience I would say
that the stability is almost the same as for i386/unstable.