Running gcc4 userland and kernel on alpha since last night.
Seems to work fine, except that sbin/disklabel/main.c needs a fix:

cc -O2  -Wall -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith 
-Wno-sign-compare -Wno-traditional -Wreturn-type -Wswitch -Wshadow 
-Wcast-qual -Wwrite-strings  -Werror -mieee      -c    main.c
cc1: warnings being treated as errors
main.c: In function 'write_bootarea':
main.c:924: warning: dereferencing type-punned pointer will break 
strict-aliasing rules
*** Error code 1

I don't know what the best fix for this is, I just compiled disklabel
with  -fno-strict-aliasing, which seems to have worked :)

-Tobias