For some reason the write speed in RAID5 is quite respectable now and what was the solution? You got me. Like I said before, the only thing that worries me is the inconsistancies with this card. I'm installing Gentoo Linux on the machine now and the drivers are ok as far as I can tell although they don't provide a kernel patch, only as a module so you can't really boot off this controller without using initrd, which is fine with me.
I still plan on making backups even with this array because RAID doesn't mean the data is completely safe, just adds another level of redundancy. The controller is now capable of sustaining a 120MB/s write speed, mine does anywhere from 100 to 150MB/s.
At this point in time, I'll probably keep it because its working but how reliable is this? I have no freakin idea. This array is just a toy at the moment as I have enough storage space across my network. If it shows decent performance in Linux, I'll probably keep it. I also need to test how well it does when it looses one drive. After Linux is installed and configured with Samba, I'll rip a drive out of the array to see how the controller handles the rebuild of the array.
I'll update this thread as I go. On that note I believe the Promise guys are reading these threads.