I owned a 2004 for a few years, which I traded in for my present Saturn Vue. The ION was a pleasure. Trouble-free, great on gas, comfortable, and well laid-out. I don't recall anything about it that would make me hesitate to buy another.
I think there was one recall on it for a turn signal pigtail or something along those lines, which Saturn fixed for free and which took about six minutes to do. Other than that, all it needed was routine maintenance and a brake job or two.
I put about 25,000 miles a year on my cars, by the way, mainly in stop-and-go NYC Metro Area traffic. So a couple of brake jobs in two years isn't out-of-line.
-Rich