I'm looking for a new board to replace my sorry-excuse-of-a-motherboard (965P DS4). Any compelling reasons NOT to go with the IP35 PRO? Is it worth the premium over the IP35 vanilla (+40€) or the IP35-E (+70)?

xTr33m sammich!,
3x RAID w/ SATA 3GB/s maximum *theoretical* burst speed is 3x 300MB/s hence the figure you're getting is way off.