1) Because it became so complicated (inertial guidance system instead of spin stabilized) the costs went up, ultimately to about $90 Million per IUS. That’s about the same price as an entire medium size rocket.

2) The IUS failed in its first flight from the shuttle – STS-6. The second of the two IUS stages failed leaving the satellite in an elliptical orbit. Fortunately the satellite had 10 times as much fuel as what it actually needed for its mission (long story) and that fuel was used with thimble-size thrusters to raise the satellite to the proper orbit over a period of several months. Another IUS on a Titan rocket also failed – it actually sent the telemetry indicating that the satellite had separated when in fact one of the cables between the upper stage and satellite were still connected!

3) At least the IUS did live up to its reputation for safety. There was one inside Challenger’s cargo bay when the accident took place. Debris from the IUS was picked up off of the ocean floor and its propellant never ignited. After the Challenger accident the decision was made to not use a much more risky Centaur upper stage for three planetary spacecraft (Magellan, Galileo, and Ulysses) and they all flew with IUSes instead.

I suspect this ad was primarily targeted at lobbiests and politicians. Before the era of commercial rockets NASA always knew which upper stages would be used for any given satellite and it was extremely rare to have a competition where multiple companies had similar enough upper stages to compete to launch a satellite.