I am in the market for some new binos and am curious about everyone's experience with the diopter adjustment. On a recent hunt I borrowed some Nikon Monarchs, which had pretty good glass but I was constantly having to re-adjust the diopter on them. It always wanted to move when sitting against my chest.

I am thinking I need some that lock, whether on the central focus knob or on the eyepiece. I've seen lots of good reviews for Vortex and have been looking at their Viper HD and Talon HD. I've heard the Talon is just as good for less money, but as far as I can tell it's diopter does NOT lock while Viper's does. One review said the Talon is very stiff however, which is their answer to the problem. What is your experience with this feature on all binos and particularly the Vortex?