I went ahead and tried it yesterday with 120 GB SSD. The answer is: it is possible. It was a bit complicated and I think it can be simplified but here is how it was done.
The gist of it is that first you follow the Intel guide and configure everything then you wipe OS from HDD and reinstall it onto left over part of SSD.
- Install both SSD and HDD into system and turn on RAID mode.
- Install OS on the HDD.
- Install all necessary drivers, namely the storage drivers
- Configure Smart Response. I used only 20G for the cache. This will split the SSD into two partitions. What's interesting is that the cache partition will be the second partition, which works out nicely for OS install
- Boot from installation media again and start setup process
- Wipe HDD partition and reinstall OS onto large SSD partition.
- Install drivers and Smart Response utility and verify that HDD is still "accelerated"
There are couple things that I am not sure about. First, whether TRIM is enabled for OS SSD partition in such configuration. Second, I think that first system installation was not necessary, and the whole caching could have been configured using BIOS utility. After I configured the caching, the computer started showing RAID config every time it boots and there is Ctrl + I shortcut to re-configure it.
Anyways, I believe this is the best possible setup for any workstation. On the second thought, you could put couple more HDDs to make it RAID 5 and then accelerate it using Smart Response.