It's been a joy to own and drive. The things you get for the price is hard to believe, even 4 years later. The hatchback styling is very Saabish and practical. The trunk is large (fits four tires perfectly) and with the seats folded, it's huge (10+ tires, full size desk, etc). The space, ride and quietness surprises everyone. Although the stock handling doesn't live up to the GT emblem, a Tiburon rear sway bar takes minutes to swap in. Reliability has been better than I expected - about one trip per year to the dealership and it's never left me stranded.
Not any feature in particular but the LONG LIST of features. Rear seat space, trunk space, quiet ride, good brakes, punchy engine, traction control, styling...
A stiffer rear sway bar for the GT, more durable paint... rear seat lighting is omitted with the sunroof. More power would be fun, but power is OK for its class already.