Found a couple of reviews for you, with relevant warnings:
"The first obvious hassle is that the My Documents folder should be moved from the C disk. In fact, any folder where you want to store files permanently can't be on the C disk. To techies like Gibson and his Security Now companion, Leo Laporte, this is no big deal. The obvious solution involves making a new hard disk partition dedicated to storing data files. For non-techie computer users however, making a new partition is dangerous and difficult. Another option is to save files to a computer or storage device elsewhere on the network.
If either of these is too much for you, consider a USB flash drive. Laptop users in particular are well-served by storing their data files on a USB flash drive, one that can stay on their person at all times.
The second obvious hassle is software updates. Software installed on the C disk constantly needs to be upgraded both to new versions and releases as well as applying bug fixes. Anti-malware software is likely to have daily updates. Microsoft has a partial solution for this, but my initial impression is that it's all but useless. Every now and then SteadyState will need to be disabled so that necessary changes can be made to the installed software."
I haven't checked this in detail but will do so and can update you after that.
Other than that SteadyState is a great thing.
