I’m on FC14 now - true confession - I’ve never done an upgrade from FC-X to FC-Y. I’ve run FC2, FC6 and now
FC14 but always started fresh each time. I think I’m going to wait another 6 months before upgrading that is until they sunset FC14 at which point I’ll probably jump to FC16.
I do keep /home on a separate partition, though, so I don't lose my data.
This laptop is brand new, though. It came with W7, so I reconfigured the HW RAID to mirror rather than striped, and threw F15 on there. It's been a very rewarding experience, with no issues for me at all.