The point was mostly to save moving around extra data needlessly. Previously, scratchpads were actually part of the USER object, so when grabbing the user data from the DB in order to do anything with it, up to 64k of scratchpad data needed to be grabbed as well, even if the purpose of getting the USER object wasnt to look at the scratchpad at all.
With the separation, this won't happen (at least when its pronounced stable enough to throw away the old scratchpad data), so there will be less needless passing around of unused data.
Also we may be able to do fun things like allow users to have multiple scratchpads, ones where they can set more specific view permissions, even share them (writeable) with others..
C.