For me it's not really about the fuel savings, since I don't put a lot of miles on my vehicles anyway. I've had my 4Runner for nearly 6 years and put barely 20k miles on it, even though it's my daily. I'm interested in the diesel because I prefer forced induction if possible because of the altitude here and type of offroading. As it is I'm a mile above sea level, and some of the trails around here are twice that high, and as it is my 4Runner struggles up hills already. Once you get to the trails, they're all slow rock crawling where the torque is a huge benefit.
I've got a coworker who custom ordered a brand new Tacoma this year and it only took two months for him to say he hates driving it and wants to trade it in because it's terrible to drive up to the ski resorts. The other two that have third gen Tacomas as well also complain about having to keep the revs up and the transmission hunting for gears all the time even after the reflash. I'll pass on that.