After reading all the glowing reports about this new lens I really started wanting it. I owned the regular f4 version in the past as well as the f2.8L. The f2.8L I had was a good lens but I was never that impressed with the f4L. I guess I didn't have the best copy of that one as this lens is crazy sharp compared to it.
That being said I'm getting a little tired of the XTi, it constantly underexposes, it's noisey even at ISO400 and focus is just hit and miss. Maybe it's operator error but I've shot enough with the other Canon bodies I've owned to know how to avoid those issues.
Anyhow here are some shots from the f4 IS taken at full zoom with a Kenko 1.4X TC on board. This thing works as good with a TC as without. (like the 300 f2.8L IS). This lens is as sharp at f4 as it is at f8 - good job Canon!