@Hermann Thanks for your comments.
The 10x42 IS sounds, by most accounts, like "the" binocular. However, weight/size have a lot of weight on my scale of preferences (FOV, close focus and other considerations having less), so I'm not sure I would be tempted. Although, knowing that they have "alpha quality" AND image stabilization makes me drool, I can only imagine the awe they must produce when using them. I find the 12x36 IS III have a good balance between weight/size/performance. I found the price a little steep, considering that they won't last like a high quality "conventional" device. A couple of years ago I gave my used SE 8x32 to my brother; I bought it used, it is a 503xxx IIRC, and he uses it a lot... and every time I bird with my brother (say 2 - 3 times a year) I'm amazed at just how well the stand the test of time: the focus wheel, the rubber armour, the lenses, amazing. After just one yer, my IS III looks way worse, and I've tried to keep it inside its case as much as possible, and not thrash them like I have other 8x32.
One idea that the IS has made evident for me is that different kinds of binoculars fulfill different goals (or work for different niche audiences). I just bird for fun, it's a hobby that I practise several times a week. On some moments of the year (like migration) every single day, but it's just a hobby, so the whole experience must be pleasurable. That's why when choosing binoculars, for me it's always "fit over performance". If it doesn't fit me, even if the performance is really good, I just don't want it. So whenever I use a 7x42 FL, or a 7x35 Nikon Porro, or my 8x32 ELSV I usually smile because the image produces pleasure in my brain (it tickles some neurons up there).
On the other hand, I guess that people who bird "professionally" (like naturalists doing surveys, etc.) need a tool to do their job (hence the original idea of this post), and "pleasure" is a secondary consideration. In this sense, I think a rugged waterproof IS (10x42 IS?) should be on top of the list, because it shows more, more detail, more chances of ID, which is what matters in this scenario at the end of the day.
With these two ideas in mind, I guess the IS III sits on the edge: it gives more, but it also "takes more", let say the set of compromises is bigger. Well, every purchase of binoculars is a set of compromises.
Say you want an amazing level of performance, brightness, sharpness, ruggedness, durability, then probably a first compromise would be price, because you are probably going to need more money than if you didn't want all that.
In other cases, say you want amazing low light performance, weight and size (of an 8x56... or an WX!) are the compromises.
If you want really lightweight and small... like in a 8x20, you have other compromises.
And then you find IS... where the level of compromises is, as said before, quite large.
At the end of the day, "there's no free lunch", as a forum member had in his/her signature.
Those are some ideas I gathered from the use of the IS III during this year. In my case, I guess the answer seems clear, since I've bought an 8x20, it's on its way, it should arrive in a few days. I don't want to have huge expectations, but being an 8x I hope the level of CA to be less than in my 12x, and the thought of being able to carry a 450 g IS 8x on a case on the belt (like one of those light 8x30, but with enhanced image) seems really attractive. Let's wait and see. I'll post my impressions.
The 10x42 IS sounds, by most accounts, like "the" binocular. However, weight/size have a lot of weight on my scale of preferences (FOV, close focus and other considerations having less), so I'm not sure I would be tempted. Although, knowing that they have "alpha quality" AND image stabilization makes me drool, I can only imagine the awe they must produce when using them. I find the 12x36 IS III have a good balance between weight/size/performance. I found the price a little steep, considering that they won't last like a high quality "conventional" device. A couple of years ago I gave my used SE 8x32 to my brother; I bought it used, it is a 503xxx IIRC, and he uses it a lot... and every time I bird with my brother (say 2 - 3 times a year) I'm amazed at just how well the stand the test of time: the focus wheel, the rubber armour, the lenses, amazing. After just one yer, my IS III looks way worse, and I've tried to keep it inside its case as much as possible, and not thrash them like I have other 8x32.
One idea that the IS has made evident for me is that different kinds of binoculars fulfill different goals (or work for different niche audiences). I just bird for fun, it's a hobby that I practise several times a week. On some moments of the year (like migration) every single day, but it's just a hobby, so the whole experience must be pleasurable. That's why when choosing binoculars, for me it's always "fit over performance". If it doesn't fit me, even if the performance is really good, I just don't want it. So whenever I use a 7x42 FL, or a 7x35 Nikon Porro, or my 8x32 ELSV I usually smile because the image produces pleasure in my brain (it tickles some neurons up there).
On the other hand, I guess that people who bird "professionally" (like naturalists doing surveys, etc.) need a tool to do their job (hence the original idea of this post), and "pleasure" is a secondary consideration. In this sense, I think a rugged waterproof IS (10x42 IS?) should be on top of the list, because it shows more, more detail, more chances of ID, which is what matters in this scenario at the end of the day.
With these two ideas in mind, I guess the IS III sits on the edge: it gives more, but it also "takes more", let say the set of compromises is bigger. Well, every purchase of binoculars is a set of compromises.
Say you want an amazing level of performance, brightness, sharpness, ruggedness, durability, then probably a first compromise would be price, because you are probably going to need more money than if you didn't want all that.
In other cases, say you want amazing low light performance, weight and size (of an 8x56... or an WX!) are the compromises.
If you want really lightweight and small... like in a 8x20, you have other compromises.
And then you find IS... where the level of compromises is, as said before, quite large.
At the end of the day, "there's no free lunch", as a forum member had in his/her signature.
Those are some ideas I gathered from the use of the IS III during this year. In my case, I guess the answer seems clear, since I've bought an 8x20, it's on its way, it should arrive in a few days. I don't want to have huge expectations, but being an 8x I hope the level of CA to be less than in my 12x, and the thought of being able to carry a 450 g IS 8x on a case on the belt (like one of those light 8x30, but with enhanced image) seems really attractive. Let's wait and see. I'll post my impressions.