From what I can tell, we won't lose our posts in either case but they will be accessed differently.  On Multiply, they come in in a bunch and it's harder to keep track of who said what.  From what I could tell anyway.  On Aimoo, it's more of the traditional format we are used to.  But the MSN stuff will be archived.  It looks like if you go to the archives, you can read our stuff exactly the way it looks now, just not post to it?  I'm not 100% sure.  I have way too much important stuff on here to risk losing any, though, so that's why I'd advise copying important stuff just in case!  Who knows if things will be lost in translation by accident - I just don't trust it.  I'm not copying everything but definitely my Christmas lists and packing lists and other things I use a lot.