Got a very observant comment on my ObjectSpaces and WinFS Part 2 entry:

My big scare is that merging ObjectSpaces and WinFS will restrict me from using OS as the persistence layer in places where the customer doesn't have and won't upgrade to the latest windows platform or even the latest SP... in these cases, I'm stuck rolling my own O/R mapping and persistence.

if OS+WinFS = use on any platform I can currently run .Net apps on without requiring an OS update, great. If not, elsewhere look must I -- and suddenly OS isn't that exciting anymore..

Yes.  We know that is a problem that we will need to solve going forward.  There are currently no specifics public details about solving that issue that I can disclose, but I want to reassure that it is a well known problem with the merger of ObjectSpaces and WinFS.