Touch time to upgrade? 1.9.14 to 2.5.1

Hi

I've been on firmware 1.9.14 for a long time. At the time each firmware was worst than the last. I found one that worked well enough for me and stuck with it. I was wondering what was the current state of the firmware and if it would be safe enough to upgrade without loosing everything on my e-reader. Is it easy to revert back to my old firmware if something goes wrong?(I'm sure I have the old firmware file somewhere.)

Thanks