With Red Hat, Red Hat Enterprise Linux 5 is supported on Itanium, while the newer Red Hat Enteprise Linux 6 is not. Oracle has also dropped support for Itanium, in a move that has led to court battle that is currently underway.
For its part, HP now has an effort underway to build the same type of mission-critical capabilities on an x86 system, as is available on the Itanium Superdome class servers running HP-UX. Codenamed Project Odyssey, the effort will eventually lead HP to favor x86 and Linux over Itanium and Unix