Interesting thread. I've been birding exclusively with Yosemite 6x30s since last summer, and while in many situations they clearly have limited reach and a relatively small "picture," they have begun to teach me (perhaps by necessity) better birding skills, and I have come to appreciate the difference between image detail and image size.
Case in point was a situation during Christmas Bird Count. My partner and I had to identify 3 dark ducks in a narrow strip of dark water on the far side of a frozen, snow-covered pond, a good 150 yards away. It has just stopped snowing, so the light was awful. I could just barely make out light-colored bills, grayish heads, darker bodies, but distrusted what I saw because, frankly, they were still *far* away. I borrowed her EL 8.5s expecting a revelation, but surprise, could make out no better detail and actually had more difficulty finding sharp focus (likely a diopter difference). They looked closer and had that nice Swaro clarity, but I couldn't see them *better.*
Like many who use budget gear, I constantly second-guess myself, wondering if more magnification, or better glass, or whatever, would help me resolve difficult IDs, but ultimately it comes down to interpreting what you see, and I find my 6x30s show me a great deal of what I need in surprisingly diverse circumstances. I do like birding the woods, and they are just stunning for chasing kinglets and woodpeckers around.
My reasons for liking this size, then, have to do with developing birding skills and not image stability (although I can appreciate that when only one hand is free). I suspect I would be happiest with a 7x for general use, and it is nice to see that venerable power being revived.