I created a USB boot drive to Clean Install my iMac with Lion. Everything worked great. I'm now going to install Lion on my MBA which I don't plan on Clean Installing. Should I re-download it from the App Store and install it that way or should I just use my USB drive to install Lion without Clean install? I'd imagine I can just use the USB key but wanted to make sure first. Assuming I do use the USB drive should I boot off it or just run the installer from the drive?