With the current QT, you can open the first file, then select all files you want to add and drag them to the window. You have to export from there, so there will be compression. At 1080p, still looks great.
QT7 will stitch together videos and re-save the combined file. You can open the first file. Then move on: open, copy, and paste each subsequent file onto the first. When you're finished, reserve the first file you've added everything too. You'll note it quickly saves instead of recompressing.
I'm not as familiar with the details Jon is discussing. I know that a QT7 file can list multiple tracks. However, using the method I described above, I ended up with ONE video track (copied and pasted over 5 additional files). It opened in Quicktime Pro (X) with no problem.