There’s now a brew formula homebrew-virt-manager which I’ve used to successfully connect to a CentOS 5 box running qemu+kvm.
brew tap jeffreywildman/homebrew-virt-manager
brew install virt-manager virt-viewer
sudo ln -s /usr/bin/python /usr/bin/python2
virt-manager -c qemu+ssh://user@libvirthost/system?socket=/var/run/libvirt/libvirt-sock