Given that we know there are compile bugs with XRC in all the v1.7 releases so far (which seems to show how few people are actually using XRC...), there are definitely "growing pains", as Ralph mentioned.
Jeff may be a little too harsh here.
The XRC compilation problems only show up if one configures with some non-default options (--enable-static or --disable-dlopen).
My recommendation is to install 1.6 and 1.7 (and eventually 1.8).
If you don't think you have the resources, then consider...
I am a user on a system (also iDataPlex, but that is irrelevant) that has stuck with Open MPI 1.4.x since it was deployed.
Since the admins have never installed a 1.5, 1.6 or 1.7 version, we instead have MULTIPLE user-built copies of Open MPI on the system, with potentially different configuration options and, of course, in "random" locations within /home. Our admins want "stable" and the users want "speed" and/or "features". Keeping both happy requires more than one version be installed.