I've come to very much like this program. I've been looking mostly for a simple but functional image viewer. I'd been using PhotoMechanic, but that was overkill for me, and updating to the newer version would be too pricy for my needs. Everyone has different needs and interests, but I've found gBrowser to be very fast and functional. It has a lot of customization options with key commands, icon and font sizes, etc. (The icons and fonts in PhotoMechanic's sidebar are teeny tiny, just as with Apple's Finder. It would seem that a lot of younger programmers simply do not comprehend what happens to your eyesight as you get older. You would think the ability to adjust these factors would be a given, but a lot of programs - including a lot of image viewing programs - do not offer this feature.)
In particular, though, I also like the responsiveness of the developer. There were a few features in gBrowser which, in retrospect, should have been obvious to me if I'd simply taken a few moments to look carefully at the preferences. Instead, I wrote to the developer to ask for help for how to work a few bells and whistles. Rather than chastising me, as some developers have, he took the time to walk me through the processes. (I once wrote to a developer about a sound editing program and asked how to do something. All he wrote to me was, "tinker with it, and you'll figure it out." I never did figure it out. That developer treated me more like an annoyance than a customer. So good customer service means a lot to me.)
I recommend that you at least give gBrowser a spin. I think the price is modest for the features and the support. And the developer seems very open to suggestions.