I just upgraded my mythtv backend's gcc from 3.4.6 to 4.1.2. It's still compiling all of world now and will be have been about 24 hours when it's all done. Then I did an emerge --sync and now there is a gcc 4.3! Arghh.
I've always touted gentoo's advantage of allowed me to run a mixed system. For a long time I was running an old version of mysql, and old kernel, and old glibc, and finally an old gcc. I would pull the odd update of certain packages if I felt like it. But the shear magnitude of the output when I would run emerge -uva world got on my nerves. I eventually caved and decided to go back to keeping an updated system. I had originally stopped updating most packages because I wanted my system to be as stable as possible (because it my MythTV machine and it records TV shows for me). At that time I was using it as a backend and as a frontend, but now I'm just using it as a backend which is a bit simpler (less room for breakage) and I'm a bit more careful now when doing upgrades. If any important packages are being updated I make sure to update them then reboot to make sure my system still boots. I also try not to fiddle with anything else. Anyways, in the case of my MythTV box I'm not longer taking advantage of Gentoo's biggest advantage, running system with mixed packages.