This is partly true.
I went ahead and backed up everything complete with a system image (I don't want to sound like a fanboy baut Microsoft implemented a very solid backup system in Windows 7). I then went on to reset the SSD to Non-RAID. This did not break my operating system.
I was able to log on and do everything, albeit with 20 gB of unused space at the end of the SSD.
I was not able to reactivate caching on the SSD but that was to be expected (because I was running the operating system on it). I went ahead and did a temporary install of Windows 7 on another (external drive) that I happened to have around (lucky me) and reactivated SRT through the Rapid Storage Technology application. At this moment my original Windows 7 install did not boot any more (Boot manager missing).
I suppose I could have tried only to fix startup with the repair disk, but I didn't want to waste any more time so I just went ahead and restored from my latest backup. Everything went along smoothly.
Note for future readers that might bump into this problem: you still need the "F6 diskette drivers" for system image restoration. The wizard does not select the appropriate driver - you must navigate to IaStor.sys (or .ini, I don't remember) and select the "generic" SATA AHCI driver (it was first on my list).