IR vs. Non-IR
Here's the scene, converted to sepia, without the IR filter:

Here's the same scene, a few minutes later (obviously with the sun having set further), but on a tripod, not quite at the same level as the original, and with a MUCH longer exposure time (8 seconds):

A couple of things to note: 1) The pollution in the sky is invisible in IR. The sky is clearer than what was seen with the naked eye, and it's darker, too. 2) the shadows have a much different quality to them.
While this scene doesn't entirely demonstrate the full effects of IR, it's interesting to see a comparison between the two images.
If you'd like to use images in this blog post, please e-mail paul(at)paulmphotography.com