I just upgraded from an old version of IMSM to the new Intel Rapid Storage Technology 9.5.
Running raid 1 on my W7 boot drive, this process was seamless. The installer automatically uninstalled IMSM, rebooted, W7 updated some configuration, and it's done.
I ended up downgrading as I had serious stability issues on the new driver.
Seems specific to the WD15EARS hard drives I had in the array as both brand-new drives ended up reporting a smart event which is extremely unlikely. My older drives were fine.