Although MSN has told us recently that they wont do an update on a weekend they have "made an exception this week." msnDude confirms the update at a WebmasterWorld thread. msnDude also explains the difference between an algorithm update and index update here.
I'm happy your site got indexed. It had nothing to do with the recent software update...
An index update, on the other hand, happens automatically -- usually at least once a day -- and no one here pays it much mind unless they're debugging a problem that might be affected by it. An index update is nothing special. Kind of like breathing; you don't think about it at all if things are going well.
Anyway, I think there has been some confusion over the difference between the two. When I say "update" I always mean "software update." I think a few people have interpreted that as meaning "index update," and that might have left a wrong impression.