I am getting ready to leave for the day and will set my iMac to do a fresh Time Machine backup, It will be a 167 Gig backup. My iTunes are on a external drive and all of my data files are on Dropbox. I am getting ready to install Lion. Hopefully, it will be next week. If not, a couple of weeks of incremental backups with Time Machine will be fine. I think my first try with Lion will be using it as an update with the backup as a safety precaution. If that doesn't work to my liking, I will do a fresh install of Lion. How many of you are prepping your machine for the big day?