Fiber Optic sites are definitely worthwhile. They really do add a lot of visibility to your peeps in low light. It is amazing how well they glow with the smallest of light.

However, just because you can see your peep well doesn't mean you have enough light to actively place that peep in the right spot on a dark-coated animal while peering through a small peep site!

I would recommend going to fiber optics, just realize they have limits.