I've just performed a clean install of CentOS 6.4 x86_64 (Minimal) along with oVirt 3.3 from the official EL6 Beta repository.  This resulted in dependency conflicts between the official oVirt repo and EPEL.

The following repositories were installed and activated:

# yum localinstall http://resources.ovirt.org/releases/ovirt-release-el6-8-1.noarch.rpm -y
# yum localinstall http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm -y

Followed by installation of the main oVirt engine and all-in-one configuration:

# yum install ovirt-engine-setup-plugin-allinone -y

This resulted in the following fatal error:

Error: Package: vdsm-4.12.1-2.el6.x86_64 (ovirt-beta)
          Requires: mom >= 0.3.2-3
          Available: mom-0.3.0-1.el6.noarch (epel)
              mom = 0.3.0-1.el6
Error: Package: glusterfs-api-3.4.0-8.el6.x86_64 (glusterfs-epel)
          Requires: glusterfs = 3.4.0-8.el6
          Available: glusterfs-3.2.7-1.el6.i686 (epel)
              glusterfs = 3.2.7-1.el6
Error: Package: vdsm-4.12.1-2.el6.x86_64 (ovirt-beta)
          Requires: glusterfs >= 3.4.0
          Available: glusterfs-3.2.7-1.el6.i686 (epel)
              glusterfs = 3.2.7-1.el6
You could try using --skip-broken to work around the problem
You could try running: rpm -Va --nofiles --nodigest

To resolve, priorities have to be set within the yum repository definitions:

# yum install yum-priorities

Adding arbitrary priorities to the oVirt and EPEL repositories rectified the issue - giving EPEL a lower value.  For example:

/etc/yum.repos.d/el6-ovirt.repo 

[ovirt-beta]
name=Beta builds of the oVirt project
baseurl=http://ovirt.org/releases/beta/rpm/EL/$releasever/
enabled=1
skip_if_unavailable=1
gpgcheck=0
priority=20
priority=20

/etc/yum.repos.d/epel.repo 

[epel]
name=Extra Packages for Enterprise Linux 6 - $basearch
#baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch
mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=$basearch
failovermethod=priority
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6
priority=25

The priority setting must be enabled for each repo definition,  Once complete, the installation succeeds without issue.

James