Had my car for almost 7 years now and I can say it has been great. Yeah, it's not a BMW, but its a easy drive, fuel efficient and has good room for the size. I recently upgraded to a high end VW Passat wagon, and even though it is classier I miss my Toyotas efficiency (wife drives it now).
Efficiency. I get 29 MPG average driving city and highway. We took a 2500 mile road trip 2 years ago and averaged 35 MPG going 75 MPH on average. It seems to only get more efficient as time goes on.
I would say styling, but I think Toyota really ramped up the corolla after 2006. The current version looks a lot cooler.