I have been able to compile and use dev-util/monodevelop-0.14 on ~amd64. I am using USE="aspnet aspnetedit firefox subversion".
I confirme. Monodevelop compile et run for me with this USEflags: "aspnet aspnetedit boo firefox java subversion -seamonkey" gentoo stephane # emerge --info Portage 2.1.3_rc8 (default-linux/amd64/2007.0, gcc-4.1.2, glibc-2.6-r0, 2.6.22-gentoo-r1 x86_64) ================================================================= System uname: 2.6.22-gentoo-r1 x86_64 Intel(R) Core(TM)2 CPU T7200 @ 2.00GHz Gentoo Base System release 1.12.10 Timestamp of tree: Fri, 20 Jul 2007 15:50:01 +0000 ccache version 2.4 [enabled] dev-java/java-config: 1.3.7, 2.0.33-r1 dev-lang/python: 2.4.4-r4 dev-python/pycrypto: 2.0.1-r5 dev-util/ccache: 2.4-r7 sys-apps/sandbox: 1.2.18.1 sys-devel/autoconf: 2.13, 2.61-r1 sys-devel/automake: 1.5, 1.6.3, 1.7.9-r1, 1.8.5-r3, 1.9.6-r2, 1.10 sys-devel/binutils: 2.17 sys-devel/gcc-config: 1.3.16 sys-devel/libtool: 1.5.24 virtual/os-headers: 2.6.22-r1 ACCEPT_KEYWORDS="amd64 ~amd64" AUTOCLEAN="yes" CBUILD="x86_64-pc-linux-gnu" CFLAGS="-O3 -pipe -march=nocona" CHOST="x86_64-pc-linux-gnu" CONFIG_PROTECT="/etc /usr/kde/3.5/env /usr/kde/3.5/share/config /usr/kde/3.5/shutdown /usr/share/X11/xkb /usr/share/config" CONFIG_PROTECT_MASK="/etc/env.d /etc/env.d/java/ /etc/gconf /etc/revdep-rebuild /etc/terminfo /etc/texmf/web2c" CXXFLAGS="-O3 -pipe -march=nocona" DISTDIR="/usr/portage/distfiles" FEATURES="ccache distlocks metadata-transfer parallel-fetch sandbox sfperms strict unmerge-orphans" GENTOO_MIRRORS="http://gentoo.tiscali.nl/ http://ftp.club-internet.fr/pub/mirrors/gentoo http://gentoo.modulix.net/gentoo/ http://mirror.ovh.net/gentoo-distfiles/" LINGUAS="fr fr_FR" MAKEOPTS="-j4" PKGDIR="/usr/portage/packages" PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --compress --force --whole-file --delete --delete-after --stats --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages --filter=H_**/files/digest-*" PORTAGE_TMPDIR="/var/tmp" PORTDIR="/usr/portage" SYNC="rsync://rsync.europe.gentoo.org/gentoo-portage" USE="X acl acpi alsa amd64 apm arts berkdb bitmap-fonts bluetooth boo cli cracklib crypt cups dbus doc dri fortran gdbm glitz gpm gtk hal iconv ipv6 isdnlog java jpeg kde kqemu libg++ lm_sensors midi mmx mudflap ncurses networkmanager nls nptl nptlonly ogg opengl openmp pam pcre perl png pppd python qt3 qt4 readline reflection sdl session spell spl sse sse2 ssl svg tcpd theora truetype-fonts type1-fonts unicode vorbis xorg xvid zlib" ALSA_CARDS="ali5451 als4000 atiixp atiixp-modem bt87x ca0106 cmipci emu10k1x ens1370 ens1371 es1938 es1968 fm801 hda-intel intel8x0 intel8x0m maestro3 trident usb-audio via82xx via82xx-modem ymfpci" ALSA_PCM_PLUGINS="adpcm alaw asym copy dmix dshare dsnoop empty extplug file hooks iec958 ioplug ladspa lfloat linear meter mulaw multi null plug rate route share shm softvol" ELIBC="glibc" INPUT_DEVICES="synaptics keyboard mouse" KERNEL="linux" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LINGUAS="fr fr_FR" USERLAND="GNU" VIDEO_CARDS="i810" Unset: CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LANG, LC_ALL, LDFLAGS, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS, PORTDIR_OVERLAY
monodevelop 0.14 is keyworded on ~amd64