While I personally don't mind carrying the 28-300L around for a day at an amusement park (and have done so, in fact), that's a Canon-centric viewpoint (not misplaced here, just saying) and Roger doesn't seem to have that mindset.
While the IQ is not as good as the Canon L-series lens, Nikon's 28-300mm FX-format lens is cheaper than both Canon's and Nikon's 17-55mm f/2.8 IS/VC offerings, and it's about the same weight and (retracted) size as those 17-55/2.8 lenses. True, it's about $400 more than the APS-C superzooms, but a FF camera is more costly, so that's not unreasonable at all, IMO, and doesn't make the 'one lens solution' club very exclusive for (Nikon) FF shooters.
Admittedly I don't know much about Nikon, so good to know someone out there has a reasonably priced superzoon for FF. Since you mention that you actually carried the 28-300L at an amusement park all day, what are your impressions of the lens (from a father's viewpoint)? I'm curious because I'd use it for pretty much the same thing. I'm guess it doesn't do so well indoors, but that's not what it's made for.