With the C2R version, you can side-by-side it with your older version (except Outlook) - which is why I opted for C2R. I said it before when I tested it with Office 2010's Technical Preview (and then later with Windows 8 Developer Preview); C2R is a slick (and sick) piece of software.
I snagged the x86 & x64 "Office Professional Plus 2013 Preview" versions from TechNet while Steve was still giving his demo. My Dl speed was over 3.5MB/s, I dig it when I slide in early before the masses get there & chew-up the bandwidth The downloads (.exe) may be 624 - 702 MB but after installing the x86 version I noticed it chewed up over 4GB of Hdd space!