So many of the things that computers are used for in the science
classroom (as opposed to data collection within the laboratory) are
designed to simulate or illustrate. This is, I feel, on of the
difficulties facing today's students they may be information rich, but
they are experience poor. While Interactive Physics may allow you to
repeat a thousand different trials varying all parameters and noting the
outcome - how many of your students haven't a clue as to how to string a
pulley system in the first place. Maybe I am a dinosaur and in the
modern world people won't need to know how to manipulate real materials,
but (other than e-mail or some forms of research) I see this push to
"net-alize" physics as just increasing this experience vs. exposure gap.