I'm astonished. Just upgraded from Quicken 6 (mid-90s vintage, so far as I can recall) to Quicken Cash Manager 2005 without any major problems. I expected the worst (and even saved a copy of the entire Quicken 6 folder on another computer), but so far everything seems to have transferred smoothly and there have been only minor glitches.
I suspect things went so well because, over the years, I used only a fraction of Quicken's capabilities and therefore had no investment files or any other complex entities. But I have to hand it to Quicken for either keeping the file formats consistent or providing good translation utilities -- I'm not sure which.
The only reason for the upgrade, by the way, was that I recently upgraded my computer from Windows 98SE to Windows XP and found that I could no longer backup Quicken across the network. Backup to floppies still worked, but there were too many floppies involved.
All of the above refers to Canadian versions of the programs, by the way.
-- Ron