Over on dtnguyen's blog, there was an interesting article on managing a telephoto to get sharp photos. Someone commented that the photo used as an example wasn't sharp, and there was a bit of a 'challenge' for a sharper photo from a telephoto. I started looking through a few photos, and although I have a lot of 'sharper' examples, they are not from telephotos, and are almost in every case a larger portion of the frame. I tried to find some that were about the same percentage of the frame. What I found was that almost all my telephoto shots (70-200 f/4) are a little less sharp than my shots from my 17-55 f/2.8. Here are a couple of examples of what I would consider typical sharp photos my lenses seem to deliver in REAL shots, either outside or in the 'studio'. Another way of saying that is that I don't think I get any sharper results in my telephoto shots (with a great lens that is very capable) than in the example enlargement.

This is from my 17-55mm at 55mm, stopped down a stop:
This is from my 70-200mm at 189mm, wide open at f/4:
Both are processed through Phase One Capture LE with no output sharpening. I didn't adjust any of the settings from the shot defaults. The top photo is a flash capture indoors, and the bottom is a sunlight/shade shot outdoor. I used a 1/250s shutter speed in the telephoto shot (plus IS), and I shoot on an APC sized sensor (Canon 20D).

I'd informally judge them to be about the same sharpness, but the bottom shot was a relatively rare find among my telephoto shots. Perhaps I tend to use the telephoto more often for 'action' shots whereas the shorter focal lengths get more use in controlled lighting situations (i.e. studio/flash). In any case I think it speaks to the need to take time to ensure sharp results from long lenses - the original point of the article.