My background is non-truck, non-offroad, somewhat heavily Corvette-based asamatteroffact, and I feel a TON of difference without the anti-sway bar. Off-road, it's a bonafide liability. On-road, I refuse to go far without it, and in fact installed the stouter XL-7 bar on my SWB truck when I put the heavier (but not that much heavier) motor in. It handles significantly better, and I often consider putting a bar on the rear, too.
Like I said, you've got to decide for yourself. Until The Man decides to legislate it, that is..