I test-drove one yesterday. It's strong, but you have to get used to shifting a little before redline, it seems that max power is from 5000-5500 RPM. The seats were a little uncomfortable and the roof was a little low, but backseat room was generous. The shifter was pretty nice, but it wasn't as smooth as the Civic Si that I also test-drove. The handling was good, but not quite as good as the Si. I liked the look of the interior better, and the cool little design touches that Toyota did to appeal to teenagers. Overall, I'd pick the tC, because it's much more livable in daily driving. There's a lot more sound-deadening material than the Si, the backseats are much roomier than the Si, there's much more down-low power so I don't have to rev all the way to 4000 RPM before I shift, and it's nearly $3000 cheaper.
Of course, I'm not buying the car; my friend is. I test-drove them to give him a second opinion, and to see for myself which one is better in case I decide to buy one. Unfortunately, he liked the Civic Si better.