Done that, although I’m worried about one part in the migration process that says something like “Announce your update to your Messenger friends”. I didn’t choose that because I want to avoid spamming their IM or mail for every updates, but does that means no update pushed to the activity feed either? At least, the Manage Connections page in Windows Live didn’t have the option to turn on or off sharing for the new WordPress.com account, only to remove it (and I really have no idea if it’s possible to re-add that thing back).
A nice thing is that it imports the blog updates as another connected activities. Users who already had another WordPress account (I did, although I doesn’t update that one very often) doesn’t have to sacrifice one to connect the other.