The RPMS provided here are for testing purposes only and are provided without warranty of any kind and without any guarantee of usability or suitability for any given purpose.
The various directories here are numbered in a forward looking manner. Aka, when I'm putting up packages that will eventually become part of RHEL5 Update 2, then you will find those packages in the directory rhel5.2. Packages from the rhel5.2 directory could then be applied to a RHEL5 Update 1 machine in order to test the forthcoming release.
It is strongly recommended that you apply updates for all the packages that are in your particular update directory. Many of the Infiniband packages have interdependencies that result in things such as the rhel5.1 ibutils not operating with the rhel5.2 opensm-libs. RPM should catch all of those interdependencies and refuse to perform an update that would break your system, but as these are pre-release packages, they may not have all the manual interdepencies listed and RPM may fail to prevent a partial update from breaking the IB stack.