It's definitely all in the eyes of the beholder - if you're coming from a D700, a Df will feel svelte, but if you're used to something like a Leica M or smaller, it'll feel a bit bulky. If you're used to a D750 (as I was when I first got to handle a Df), the lack of a pronounced grip will feel off. And if you're used to carrying cameras on a strap and/or by the lens, a Df, even with one of the bulkier zooms, will not feel overly heavy because it objectively isn't (again, especially when coming from a D700), but if you like carrying cameras "by the body" (i.e. - at least in my case - in the right hand, dangling or otherwise), a Df with 24-70 (Nikon or Tamron/Sigma? There's quite a big difference) will feel really unwieldy.
Which reminds me that once upon a time, I had planned on doing a kind of overview of how to carry a camera in hand ... not that it mattered to many people, but what kind of grip a camera feels comfortable with *is* important to me personally. And I remember *not* really finding a way to grip the Df without it feeling either very uncomfortable or unsafe. But that's definitely just me - because I walk around with the camera in the (right) hand, no straps (apart from a wrist strap if necessary and/or applicable). Of course, I will use neck straps with bigger lenses, but only reluctantly (if possible, I prefer carrying a bag or backpack to put the camera in in such a case).
Again, what works how well will completely depend on your habits and preferences. That said, I'd never expect a D700 to outdo a Df anyway - except maybe in terms of Af, and then only maybe; the D700 is a great body, but really big and heavy, too, so carrying *it* will not be any nicer over time than carrying the Df. However, the D750 still holds the crown of most comfortable Nikon body *in the hand* when it comes to DSLRs; I've even walked around with the 70-200mm f/4G on it in hand - not too big a deal (if you can put it into the backpack from time to time if it gets too heavy). The D750 is a very, very well thought out camera indeed - nothing special, but almost everything eminently usable.
But the Df's mix of great sensor and really pretty compact body is still unique and enticing in its own way. Ever since owning the Z fc (which is kind of a spiritual successor to the Df), I've had flashes of wanting to try the Df again. But then, I also get that with the M10-R and M11 - and it all goes away again pretty quickly ...
M.