I'm considering getting Office 2011 for my new MBA. Many e-tailers are selling the 3-machine version of H&S for about $5 more than the single-license version. I already have Office 2008 on my iMac. What happens if I install 2011 on that machine? It just replaces the 2008 stuff, right? It's been so long since I did that kind of upgrade -- and then on a Windows machine -- that I can't remember how the process works.