A fairly popular outdoor writer, John Barsness has written that for open country glassing, he prefers 12x glass. Though, in the same article he suggests 8x as the best all-around option for beginners and indicates that his go-to glass is a 10x.
Stability is really a fairly subjective issue. We had a fairly lengthy debate about this earlier this year. What it comes down to (I think) is that some people have trouble holding higher magnification glass steady while others don't. 12x glass could be really nice, if you are glassing rather open terrain and you have the ability to hold them steady (especially after a long hike or a sprint up a mountain, etc.) or if you're going to be mounting them on a tripod, window mount, etc.
Stability issues aside, ther are two things you should also keep in mind as you consider the 12x option.
- 12x glass will be bigger and heavier than lower magnification binoculars. This will make them more cumbersome, especially after a hard day's (or longer) hunting. They will also have a smaller Field of View, which may be bothersome to you. Only you can decide.
- Making quality optics of high magnification (10x+) is not easy. It requires greater skill and precision to manufacture than lower magnification units. I have noted before that in mid-priced glass, the 8x and lower units tend to be of pretty high quality whereas the 10x+ binoculars show a lot more variation in their quality. It's really a hit-and-miss affair and making sure you get a good sample can be difficult.
Birdwatcher is absolutely correct; I do feel that the Nikon Monarch is one of the best binocular deals available but, I have not seen their 12x glass so, I don't know if they are as good as their low-powered siblings. Part of this will (of course) depend on how demanding you are with your optics. My friend is probably going to buy one of the 12x56s pretty soon so, I'll get a chance to see them in the (hopefully) near future.