I'd say that because you've got raptors, you're system will still feel nippy (due to the reduced latency vs regular drives), which you can argue is the main thing to have.
Boot time should be about the same due to being able to not have to initalise the array on startup.
Disk to disk transffers are going to slow down, installing programs and load times will also slow down, but I think with program loads, it'll not be a huge amount of difference either way.
The only time you might notice it is if you're doing a disk intensive operation that is doing lots of reading/writing (editing high res video comes to mind).
Dan