I've had my D700 only since just before Christmas. I dropped my D200 on the floor, and although I got it checked out by the Nikon Service Centre, I wasn't convinced there was no internal damage (it hit the floor sufficiently hard to dent the wide angle lens that I had on it) so decided it was time to upgrade. I was initially going to go for the D300, but eventually decided to splash out for the full frame D700, and I'm glad I did. The quality is great and the ability to crop hard and still get good photos is one of the things I really like with the FX model.
For example, you see the white temple in the middle of this post (tucked away in the trees, just left of centre). Well, I cropped that out and got quite a passable 500x350 photo for the web from it - certainly as good as anything you would get from a P&S close to the temple - and my guess is that I was using only about 2-3% of the frame!
I haven't seen the 28-70mm lens. It is not available in Malaysia. Only the 24-70mm is. I am a bit puzzled re your comment about the weight. According to the Nikon website here, the 28-70mm weighs 935g whilst my 24-70mm weighs 900g - so mine is a fraction lighter than yours. Or could we be talking about a different lens?
Cheers . . . David