2 years ago (or so) I went from classic to 7.x... it was a bit intense as there were actually 2 upgrades I had to do. I lost a little bit of data between the two (but not a whole heck of a lot). The files I lost had been corrupted, and the links to smilies etc. was lost, however it was very easy to do and took a couple of hours (due to the host at the time being very slow). Other than that Rick and crew do a great job writing upgraders that actually get the job done quick and clean.