Last summer I had an ION for a business trip from Orange County to the Silicon Valley and back. It's a long trip that puts a car through a lot of scenarios: the worst of LA traffic hell, two mountain ranges, a vast expanse of flat highway, and twisty country roads around Gilroy (garlic capital of the world!).
The ION's exterior styling fits with Saturn's current design trends of understated geometric designs and vaguely European modernism. I think it's handsome for a small economy car, but that's subjective. The interior continues the geometric theme of circles, arcs, and ellipses. Mine was furnished with grey cloth, hard grey plastic, and silvery gray accents. It is thoroughly unexciting, but that's to be expected in a value-oriented economy car. The gauges are mounted in a center pod and have a classic-looking typeface. I expected the location to be distracting but after a few minutes it became second nature.
The ION seems to be tuned to drive like a larger car. The steering has a heavy feel and mushy center. It's easy to keep pointed on the highway but can be annoying in city driving. The suspension is incredibly loose for a car this size -- on the highway it's dreamboat smooth, but there is an immense amount of body lean on onramps or even 90 degree turns from a stop. Acceleration is good for a car in this class and I had no problem merging, passing, or climbing hills. The engine is very loud and coarse-sounding, especially at higher RPMs. I found myself limiting throttle just to avoid the noise, which would get grating in a daily commute. The ION automatic is rated at 24/32 mpg. I lost my mileage log but recall getting mileage consistent with those numbers.
The interior ergonomics are generally fair. It has a high door sill that's easy to trip on, and the cup holders are positioned such that a medium-sized fast food cup will block all the HVAC controls. The AC is surprisingly powerful, which is common for GM vehicles. Visibility is good.
There was a lot riding on the ION's 2003 debut. Saturn had been waiting a very long time for an updated compact car, and the ION was the first example of GM's Delta-body / Ecotec engine combo that would be the basis of small GM cars for years to come. The ION was unilaterally slammed as a horrible failure, which I think is unfair. It's the same size as a Cobalt or Corolla, and compared unfavorably in that class. But it was actually priced priced closer to an Aveo or ECHO, and looks good against those. I would also argue that the outgoing S-series was meeting consumer expectations better than the Cavalier was, so the incremental S-to-ION transition was easily upstaged by the earth-shaking Cavalier-to-Cobalt transition.
The ION was the last model designed around Saturn's original ethos of friendly, economical basic transportation. It lives up to that promise. It drives like a floaty midsize car and gets compact car mileage. It's not flashy or fun to drive, but that's not the point. It would be a fine choice as an everyday car, especially for someone who is downsizing from a larger vehicle or doesn't really care about cars. Conventional wisdom is that a Civic or Corolla does this better. That's probably right, but only by a thin margin. The ION's price advantage makes it a defensible choice.