I got a pair of the 12x NLs, what sold me was the FOV is the same as a pair of 10x50 ELs, which is what I was using before. (The 10x50 ELs are for sale in the classifieds if anyone wants to jump on that.) I was always unsure about giving up FOV for more power, but the NLs FOV spec made it seem like a no brainer. Same FOV with 20% more power? You bet, sign me up.
I have been very impressed with the 12s. I was a little concerned about hand shake as well, but the few times I have had them out turkey hunting (not quite the same test as a high country mule deer or elk hunt, but field experience free handing them none the less) it has not been an issue for me. I did not get the forehead rest with them. I would say that I can free hand the 12x42s as well as I could my 10x50s and the reason for it is the ergonomics of the NLs. I thought it was more of marketing gimmick from Swarovski than an actual benefit, but it helps. Hard to explain without feeling them and experiencing it for yourself, but they just fit in your hands so nice and it makes it easier to handhold, I think. My ELs felt blocky after switching back and forth between the two. Now, granted, I haven't done a ton of looking through them freehand past maybe more than 1,200-1,500 yards, but if I am looking that far or farther for any period of time longer than a few minutes they are going on a tripod anyway.
I had read a few other users describe looking through the NLs as "the eyebox is pickier than ELs," meaning it was hard to get a good picture due to eye relief causing shadow or black spots. I would agree with this AT FIRST, because they do take a little getting used to. After I had my diopter and eye cups set and was used to pulling them up to my face where they needed to be, it was a non issue.
Over all I really like them, can't wait to get some use off a tripod with them. 10s are awesome, but I felt like I wanted more bino on several occasions while glassing off a tripod on some of my hunts and I didn't want to own and carry 15s and 10s. 12s fit the bill for me really well and I have been pleased with the large FOV, steadiness when free handing, and overall performance. The image is crystal clear and looks amazing edge to edge.