You need to understand the information behind the rating.... As a reader of CR for 30 years, I have a little insight. For 2005 model year vehicles in general, there are very few "problems" in this day and age - most problems show up a few years down the road. So in the 1st year, it does not take much for a very reliable automobile to rate "average" if there are any problems in even oneof the dozen or so categories that CR looks at.
In this case, I suspect that the "body integrity" category dragged the overall rating down to average. (If you haven't heard about the rattles & squeaks in the rear hatch and moonroof, or possible problems with the wind deflector or moonroof glass, you have not been reading these forums very much.) I say "suspect" because I haven't actually seen the details of the ratings yet myself - that will show up in the 2006 handbook that comes out next month, and in the April '06 auto issue. Remember, the only thing that's really new about this car IS the body (the chassis comes from the European Avensis, and the drive train comes from the Camry - both proven commodities).
However, to help reduce your worries... CR actually reviewed the tC in its December issue (on newstands now) in the sport coupe category. While it didn't rank at the top (and for the particular evaluation criteria used, it shouldn't), it was rated highest in value, ride, and comfort, and high for a few other things. PLUS, it's one of the few cars they recommended. DRIVE AND ENJOY!!