...who is a dietician by trade, says something to the effect of, "Move more, eat less; that'll be $200, thank you," to friends who ask how to lose weight and get more fit when they don't have serious health issues.
Seriously, yes, specificity helps with training for a specific demand (hiking helps hiking, running helps running, lifting helps lifting, etc.), but any kind of exercise helps total health (provided you don't over-train to injury levels). Do something, even if it's just mowing the lawn or going for a walk after dinner.
Personally, I run, I bike, I lift (a lot, recently, actually), I interval train, I swim, and I'm still not where I'd like to be for general fitness. That ladder is a long climb when one's spent the previous decade not doing much.
That being said, I'm in the same range of fitness as most of the folks I work with--and there are some serious athletes working in a pizza place, of all things (never figured on that, but I guess it's a byproduct of needing a personality that likes stress to last in that sort of environment). One guy is training to run a sub-three-hour marathon right now, one's body building to become a professional wrestler (and squats 140%+ of his body weight on a regular basis), one is a regular rock climber, two of 'em are martial arts instructors on the side, etc. I try to work out with one of 'em at least once a month, and it's really helpful to see all of the different ways to work a body.
Work hard, play hard, go home happy. Not a difficult proposition.
Back on-topic, I've run into good and bad things from minimalist shoes for running.
They've taught me proper stride and foot strike technique, improved my ground awareness (definitely helping to avoid injury on some of the trails I've run), helped with my shin splints (as a byproduct of not landing on my heels as much), and definitely toughened the muscles in my feet (I used to get pinkie toe cramps after long days on trail; I don't anymore). On the other hand, I have managed to pull muscles in my feet when over training on pavement, and I did manage to stress fracture a tarsal bone two months ago when I stepped wrong coming downhill (sprinting) onto a large root.
That's healed, now, and I've learned a few things about how to take downhills better because of it. I ran my first half-marathon in minimalist shoes, and I know I'll get back there in six to twelve weeks.
However, minimalist shoes are most definitely not for everyone, and I wouldn't recommend them without taking the time to adjust before running longer distances. About 20% of my training (one day in five) was in minimalist footwear when I started running. Every week, I would increase my mileage and reduce the amount of time I was in "traditional" (think post-Nike) footwear by a bit until I was running all of it in minimalist shoes. My feet are tougher, my stride is better, and my cardio has benefited from doing so. That doesn't mean that they don't still have challenges associated with 'em, and I try to be very aware of their limitations. Just like the limitations associated with any piece of equipment--be it issued by genetics or by greenbacks.