The Deep Space 1 was the first in a series of two ships launched by NASA as part of their New Millennium Program. It had the important, yet uninteresting task of testing new technologies, in an attempt by NASA to keep future missions within their budget limits. The most notable of these technologies was the NSTAR electrostatic ion thruster. Ion Thrusters work by exerting small amounts of thrust over long periods of time, making them fairly fuel efficient. As such, the NSTAR, if it worked,would roughly half the amount of mass of fuel needed for a mission, meaning either cheaper launches, or longer range missions, bother positive results.
Another important technology to be tested by Deep Space 1 was the SCARLET (Solar Concentrator Array of Refractive Linear Element Technologies) - basically very well made solar panels, designed to work in the depths of space. These were innovative as they generated more power for less area than previous panels, producing similar (although on a smaller scale) as the NSTAR.
Although many smaller technologies, such as the Small Deep-Space Transponder and the Plasma Experiment for Planetary Exploration were included in the flight, the only other truly groundbreaking devise was the "AutoNav" Most spacecraft are tracked whilst in space by the Deep Space Network (DNS) which works by satellites pointing away from instead of towards earth, and keeping an eye on the probe. This has the disadvantage of using up both human time, and a lot of satellite hours. The DNS worked by targeting bright objects (such as asteroids) and using it's distance from two of them, to calculate it's distance to another.
The Deep-Space 1 was actually an incredible success, with the only major failure being that of the Remote Agent (an artificial intelligence designed to steer the spacecraft ). It was unsuccessful, but the only issue that arose from this was missing a chance to photograph a comet.
The NSTAR failed initially, after only four and a half minutes into it's flight, but a little work on the electronics brought it on-line, and it functioned for a further 678 days afterwards. The success of the engine caused it to be implemented in the Dawn mission (a robotics controlled mission launched in 2007 to visit the dwarf planet Ceres in the asteroid belt).
The "AutoNav" worked superbly, requiring only minimal input from humans to adjust brightness, and in fact, most spacecraft today are using similar, more advanced versions of the same technology.
Deep Space made passes of all but one of it's intended comet targets, and the strength of it's ion engine allowed it to correct and continue with the mission, even after a collision with an asteroid without any debris shield. The mission controller, Dr. Marc Rayman gave a briefing at the end of the mission, in which he stated that Deep Space 1 had "performed well"
Dr. Marc Rayman, "Mission Log", http://nmp.nasa.gov/ds1/
Boeing, "NSTAR Ion Engine", http://www.boeing.com/defense-space/
Wikipedia, "Deep Space 1", http://en.wikipedia.org/wiki/Deep_Space_1