i'm not sure about the 40d, but the 7d has an electronic level that will help you get your verticals and horizons straight. or you could try lightroom 5's new verticals correction.
i like the colors too, and i like how you've got the reflection of the sun and building in the windows. the diagonal lines on the brown building appear to be pointing at the reflections.
The building on the right is pretty straight...that's how I lined the camera up (didn't check level on camera though) during the shot but the lense distorted it a little. The building behind is much further away...and taller. The left side of the building looks slanted to the center and I assume that's what you are talking about...right?
So...are you saying that both buildings should be slanted toward the center equally which would mean no true vertical?
Obviously it is nice to get all the perspectives etc correct in-camera but without tilt and shift you can only get your image level (and vertical if relevant). However, in post-processing you can correct the verticals if that is what you want from the image. To me, this one looked like it needed some correction as there was no one reference point.
If you open the image in PS and select the whole image with the marquee tool, you can then use Edit/Transform/Distort to correct the various elements (I find this more effective that Transform/Perspective. You can overlay a grid with either Ctrl' (Windows) or Cmd' (Mac OS) to help. Here is a screen grab of the correction I made showing the stretched marquee (dotted frame).
nicely done pete. i've been playing with the verticals button in lr 5, it does a nice job most of the time. but it's good to know how to do it when the auto button fails.
I agree with the others about the verticals. That said, its a bonnie fotie to begin with. Intense sky, the flare, the contrasting colors. All very good. Nice shot, Glenn.