I don't quite follow the f4.3 thing. It sounds like a thought left short or a misunderstanding of crop factor vs. low light vs max f-stop.
I have the older 24-85mm ED 3.5-4.5 that I am surprised no one has mentioned. It is a very solid performer, even at macro work. From what I can tell, the design is very similar but greatly updated with the new tech that has came along. If it performs better than that - it will be a great compact lens for sure. Add a 70-300vr and you have a hell of a travel kit.
A couple of things to note that I have found:
VR is 10x better than f2.8 unless you are always shooting in the dark. Reason: You get VR at all F-stops and most images in good light or you want sharp are usually at f/5.6-11. The gain with VR is much greater than just 1/2-1 (or so) stop of light.
Add to that, if you are shooting groups, 2.8 usually leaves people out of focus and you end up stopping down anyway - that is usually where the trouble begins. VR - helps that.
Comparing this lens with Nikon's 24-70 is fruitless. Like comparing a Smart car with a Cadillac. Comparing it to the 24-120vr f4 - could be ok, but that is a "gold ring" lens which indicates better quality plus it is twice as much.
3-party: Tamron's 24-70VC is $1,300, Sigma's 2.8 is $800. Tamron's 28-75mm f 2.8 @ $500 is the only one that is an option if you are on a budget. But there again, the VR in my mind is worth the $100 more and the loss of a stop of light. Some like 3-party lenses and have good luck with them. Outside of Tokina or primes - I have not had good luck. For the most part, 3-party Pro glass is usually good.
One thing that is left out is that many times Nikon's bodies and software auto correct CAs and even vignetting where they do not with 3-party lenses. Not a huge thing, but nice and a bit of a time saver - especially if you have 1,000s of shots.
2.8 glass is desirable and yes many shoot it. Why? It is the most durable, most advanced, best glass, highest quality assurance, best internal parts, can withstand the elements and made for years of everyday use. The 2.8 is an added bonus in my mind and not the primary factor.
I'm willing to bet most shooters shoot at f4-f11 for the most part. At that point, the 2.8 doesn't mean much. So then comes the build quality, and Nikon's lower end glass is just as good as the 3-party pro glass in many cases. If you are on a budget and there happens to be a Nikon VR lens, with ED, that is also designed for video? If that doesn't fit the ticket, I'm not sure what would.
