The big downside of fat bikes is definitely the price (especially for wheels and tires). Ti is normally out of my budget, too, but I scored this used one for the price of a new aluminum one.
Several years ago, when I tried a fat bike for the first time, I wasn't sold on the idea of dropping that much coin on something that weighed much more than my heaviest mtb and seemed limited to just a few snowy weeks out of the year.
But, the weights have been coming down a bit, due largely to lighter tire offerings, and I eventually realized that fat bikes are great for all sorts of terrain: mud, loose dirt and sand, ice, roots, rock gardens. The monster tires give you crazy traction and they roll over obstacles so easily that choosing the right line becomes much less important. I now find myself casually rolling over stuff that used to make me really nervous.
If you get a chance, take one for a spin. You'll probably dig it.