No, the biggest problems for me came from kde, qt, and myth. kde 4 has finally gone into the stable tree, but that caused me all kinds of issues as so many things are dependent on the kde3 libs, creating blocks. In theory that shouldn't happen with slots, but part of the problem is that multiple packages from kde3 were aggregated into singles in kde4, and vice versa. MythTV .22 now runs off QT4 entirely I believe, and there were lots of blocks between the Myth versions. Packages moved there too, with MythDVD being removed and integrated into MythTV and mythtv-themes causing weird blocking issues.
Also, I am running portage 2.2 (which is hard masked... don't try it newbies). I needed this to be able to use certain new functionality and install some needed software. I am a bit frustrated with Gentoo over the last year or two in terms of how badly they've done at getting kde 4 stabilized and transitioning to the new portage.
Also, compiz is a running issue for me. In my futile attempt to move back to the stable tree, I always unmask a specific package version only, e.g. compiz-fusion 0.8.4, so that as that version goes stable, it won't keep moving me to a new unstable version, and eventually I can remove it from package.mask, so I had to update all the various packages that are dependent on compiz-fusion.
Portage now uses a license restriction, so had to fix ACCEPT_LICENSE in make.conf, just using * for now.
Had a profile change (that was pretty recent), so that makes lots of things not work.
I went through and manually cleaned out package.keywords, package.use, package.provided, package.mask, and package.unmask.
Of course, had to run revdep-rebuild, emerge --depclean, emerge @preserved-rebuild many times. A few packages wouldn't build at all, so I just removed them and will re-add later (xine-lib comes to mind). TONS of broken library connections and dependencies on older versions of libraries. You won't have to worry about @preserved-rebuild if you aren't using portage 2.2. The @ denotes a set, which is not present in older versions of portage.
Lastly, I use the +doc useflag... again, don't do this newbies. You'd think it would be harmless, but you'd be wrong. Nothing creates more issues than the doc useflag.