I have tried xmoto on amd64 2006.1 gentoo release. Works great, with good sound and video. Using Athlon64 X2 4200+, NForce4 Geforce 6100, Sound Blaster Live!. Currently this package is masked, but it seems to work perfectly.
Stable on x86, no (real) bugs open, emerges and works fine for me. Portage 2.1.1-r1 (default-linux/amd64/2006.1/desktop, gcc-4.1.1, glibc-2.4-r3, 2.6.18-suspend2-Dudebox-Edition x86_64) ================================================================= System uname: 2.6.18-suspend2-Dudebox-Edition x86_64 AMD Athlon(tm) 64 Processor 3200+ Gentoo Base System version 1.12.6 Last Sync: Mon, 06 Nov 2006 14:00:01 +0000 distcc 2.18.3 x86_64-pc-linux-gnu (protocols 1 and 2) (default port 3632) [enabled] ccache version 2.3 [enabled] app-admin/eselect-compiler: [Not Present] dev-java/java-config: 1.3.7, 2.0.30 dev-lang/python: 2.4.3-r4 dev-python/pycrypto: 2.0.1-r5 dev-util/ccache: 2.3 dev-util/confcache: [Not Present] sys-apps/sandbox: 1.2.17 sys-devel/autoconf: 2.13, 2.60 sys-devel/automake: 1.4_p6, 1.5, 1.6.3, 1.7.9-r1, 1.8.5-r3, 1.9.6-r2 sys-devel/binutils: 2.16.1-r3 sys-devel/gcc-config: 1.3.13-r4 sys-devel/libtool: 1.5.22 virtual/os-headers: 2.6.11-r2 ACCEPT_KEYWORDS="amd64" AUTOCLEAN="yes" CBUILD="x86_64-pc-linux-gnu" CFLAGS="-march=k8 -msse3 -Os -pipe" 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 /var/qmail/control" CONFIG_PROTECT_MASK="/etc/env.d /etc/env.d/java/ /etc/gconf /etc/java-config/vms/ /etc/revdep-rebuild /etc/terminfo" CXXFLAGS="-march=k8 -msse3 -Os -pipe" DISTDIR="/usr/portage/distfiles" FEATURES="autoconfig ccache collision-protect distcc distlocks metadata-transfer multilib-strict parallel-fetch sandbox sfperms strict test" GENTOO_MIRRORS="ftp://linux.rz.ruhr-uni-bochum.de/gentoo-mirror/ ftp:///ftp-stud.fht-esslingen.de/pub/Mirrors/gentoo/" LDFLAGS="-Wl,-O1" 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'" PORTAGE_TMPDIR="/var/tmp" PORTDIR="/usr/portage" PORTDIR_OVERLAY="/usr/local/portage_overlay" SYNC="rsync://server/gentoo-portage" USE="amd64 X alsa apache2 berkdb bitmap-fonts cairo cdr cli cracklib crypt cups dbus dlloader dri dvd dvdr eds elibc_glibc emboss encode esd fam firefox fortran gcj gdbm gif gpm gstreamer gtk gtk2 hal iconv imap input_devices_keyboard input_devices_mouse isdnlog jpeg kde kdeenablefinal kdehiddenvisibility kernel_linux libg++ mad mikmod mp3 mpeg mysql ncurses nls nptl nptlonly objc objc++ ogg oss pam pcre perl png ppds pppd python qt3 qt4 quicktime readline reflection sdl session spell spl sqlite ssl tcpd test truetype truetype-fonts type1-fonts udev unicode userland_GNU video_cards_radeon vorbis xml xorg xv zlib" Unset: CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LANG, LC_ALL, LINGUAS, PORTAGE_RSYNC_EXTRA_OPTS
stable on amd64 thanks for reporting