first of all, mouse cursors should never obstruct, they should help with orientation. the purpose of a mouse pointer is, to allow the user to focus on special small areas for interaction.
i found another thread in ubuntuforums, discussing something like our topic.. a user was complaining about the passive mouse pointer stealing focus from the users interactive attention focal point..
see: http://ubuntuforums.org/showthread.php?t=1343444
i think "enhancements around the human's UI experience" is the true topic title of this..
thinking of the user experience, it's like conducting a vehicle through a traffic environment of unmanaged information and code.
the tools available to maneouver such a grid of possible routes are all to be designed in order to facilitate the travel into one direction at a time:
the focal point.
the human focal point being a dynamic property, is the actual point of reference for any reasonably thinking desktop designer.. the next to kin is "imaginable virtual focal points", like the once deriving of Fitt's law.
to mention the mouse pointer's behaviour in this context is like questioning the elementary ethics of what "usability" should mean..
we have been discussing how panels will be designed in the future, diogonally opposing corners of the desktop will serve diaogonally opposed hot-corner purposes:
top-left - bottom right interaction - information
that's great and has something to do with window management and wrapping a "shell" around a hard core of logical functionality.
i suggest let's talk about the actual logical functionality of the human's focal point at the computer.. if a little excourse into human interface philosophy may be granted..