I have been working with a client on setting up multipath for some Linux database hosts, with a NetApp FC Backend. They wanted to use Ubuntu 8.04 and after mucking a bit with the official config from NetApp (had to change path_checker to directio as readsector0 does not work on Ubuntu, and disable priority check as this doesn't work either :( )
Ubuntu then saw the 4 paths, but as we soon discovered, it returned IO errors if just 1 path failed, which made the kernel remount read-only :(
Also, the lack of netapp priority support made NetApp boxes complain about the box using suboptimal paths all the time (two of the paths went through the other controller and are only supposed to be failover paths).
We then tested on CentOS (Red Hat/RHEL derivative) 5, and it worked perfectly - with readsector0 and netapp priority support.
Needless to say - the customer decided to switch to using CentOS for SAN attached hosts :)