Classic compiler, lots of support on many platforms. More-recent versions not rock solid yet. Benefits from linux coverage. Picky compiler, some bugs, mainly worked-around with autoconf. Built in performance tools.
Builds are painfully slow.
Anyone who wants to run the code you've compiled will need this patch as well. If both a gnu compiler and non-gnu compiler are in your path, the gnu compiler takes precedence in the preconfig test. Otherwise, the build may fail trying to pull in the wrong libiostream. These issues are still being identified. See Bugzilla bug 20297 for some discussion.