The "feel" of the tires will change once you put the Mr. Tuffy's in. I agree with the comment that they work well when installed correctly, the other side of the argument is, if they are installed incorrectly, they can cause more flats than they prevent by chafing or pinching the tube.

A better solution is to find a tire with adequate puncture protection built into the tire. There is always a trade-off however. Tires that have exceptional puncture protection will generally be heavier and provide a less dynamic ride, or they can be very expensive. Most mainstream tire manufacturers make an array of options.