I guess I'm right at the upper end of that target market then! Kinda funny as I first told myself I wouldn't ever buy a 5th Gen with the new ('14+) front end, and now here I am. It did nothing for me in certain colors, but the grey I really like. I guess ironically, my 4th Gen I just traded was the first 4R I'd ever driven, and at the time I was thinking about a Tundra, and told myself I didn't want a 4R; I ended up buying it 2 weeks later, and loving it!
As for the 5th vs. 4th Gen, yes, the suspension, brakes, quiet ride are pretty sweet, as are all of the electronics on the dash, and updated "stuff". We test drove a Highlander and 4Runner before making this purchase, as the 4Runner is my wife's daily driver, and we needed to do our due diligence, but both never hesitated with the decision to buy the 4Runner. It hasn't seen anything but pavement yet, so all of my comments would be daily-driver related, but with your mention of lighter materials - the tailgate is noticeably lighter (or easier to close - could just be the struts).
Will keep you all tuned...