If you want speed, go for SSDs (I know that prices are still high).
Here is some info from Wiki - RAID 0+1: striped sets in a mirrored set (minimum four disks; even number of disks) provides fault tolerance and improved performance but increases complexity.
The key difference from RAID 1+0 is that RAID 0+1 creates a second striped set to mirror a primary striped set. The array continues to operate with one or more drives failed in the same mirror set, but if drives fail on both sides of the mirror the data on the RAID system is lost.
This will explain better: http://en.wikipedia.org/wiki/RAID
I have my OS (Win 7 64-bit) and all programs on one single 750GB (overkill, but I had it around) drive. My data is on two 1TB disks set up in RAID1 (mirroring).
Reply to your last question. Read as well as write is slightly faster in RAID0 as compared to RAID1. But at today's high speeds, is this really noticeable?