What we've done is to set up the NFS, but we mount the entire perl distribution. That way we get rid of the 5.6 vs 5.8 complaints - all machines will have access to 5.8.7 (the version we standardised on).
We installed them with binaries in separate directories, but the modules all are installed to the same location. For pure-perl modules, this obviously works very easily. For XS-based modules, this means we need to compile/install once for each platform we support (AIX, Sun/SPARC, HP/PARISC, HP/IPF, Linux/ia32, Linux/ia64, Linux/x64, Linux/ppc64, Linux/390x). It's a bit of work, but it does mean that all of our machines always have access to everything. Or none of them do.