After making minor changes to the Ion in 2004, Saturn decided to step up the Ion's evolution for 2005.  Perhaps the most visible update came in the transition from continuously variable transmission (CVT) in the coupes and 5 speed automatic in the sedans to uniform optional 4 speed automatic in the 5 non-Red Line trims.  This switch paralleled the change in the 2005 Saturn VUE and showed a commitment to better handling and feel over nominally advanced technology.  Saturn also made the seats more comfortable and the steering wheel bigger.  Other mechanical changes included improved suspension and steering, reduced road noise, and a more elegant exterior.  
Despite the changes, the 2005 Saturn Ion has kept its core features.  All 5 non-Red Line trims have a 2.2 L, 140 hp I4 engine and get 25 mpg in the city, 34 mpg on the highway.  The 4 door coupes seat 4 and have 14.2 cubic feet in the trunk.  The sedans seat 5 and have 14.7 cubic feet of cargo space.  
Overall, the Saturn Ion made significant improvements in 2005.  Reviewers appreciate that Saturn has addressed its weaknesses while continuing to deliver solid performance for drivers on a budget.  As with previous models, users would like to see better materials for the interior and a more refined look for the exterior.  Otherwise, the 2005 Saturn Ion took some very important steps in catching the competition and establishing its place in the pantheon of compact models.