These systems are now in place and both are performing as expected. I had one issue with both of them.

The processors had stepping issues as the XP used a newer version than MP. A BIOS update took care of it. As they added XP support (supposedly single processor only, but does support in multi-processor)

Company now wants 2 more machines with the 3ware controllers.

We actually tested problems. We pulled a drive out, let the hot-spare kick-in... then pulled another. Wiped those two drives pulled out on another machine (dd if=/dev/zero of=/dev/hdb bs=1024 count=80000000 or so...), put them back in... used the tools that are available... rebuilt the array whilst being accessed, and designated a new hot-spare.

All seemed to work as expected.