Repeat after me:
RAID/mirroring IS NOT A SUBSTITUTE FOR BACKUPS!
RAID/mirroring IS NOT A SUBSTITUTE FOR BACKUPS!
RAID/mirroring IS NOT A SUBSTITUTE FOR BACKUPS!
RAID/mirroring IS NOT A SUBSTITUTE FOR BACKUPS!
RAID/mirroring IS NOT A SUBSTITUTE FOR BACKUPS!
RAID/mirroring IS NOT A SUBSTITUTE FOR BACKUPS!
RAID/mirroring IS NOT A SUBSTITUTE FOR BACKUPS!
mirroring is great, and I wouldn't be without it. But it's only useful to guard against data loss in case of harddrive crash - it doesn't save you from errant deletes, viruses, filesystem crashes et cetera.
Multiple partitions is a good thing, since you only lose one partition in case of filesystem corruption. Granted, filesystem corruption doesn't happen often if you run NTFS, but it CAN happen, and when it does it usually hits you hard. VERY hard.
A separate partition for your paging file is nonsense. It only helps if you put it on a separate physical drive. Besides, you should have enough RAM that you don't need a paging file (which is, of course, impossible if you use anything from Adobe ;-) )
I have a partition for OS + apps, one for documents and source code, one for games and then a "dump" partition. When I get the time to back up stuff etc., I'll merge games and "dump" since there's not much point in having them separate. "dump" is where I have temp files, downloads, misc. large data files et cetera.