I think there are a few things coming together to make your picture look a little soft. And while the 100% crop you showed isn't tack-sharp, I don't think a top-of-the-line lens at the same focal length would really perform much better if put to the same test (more accurately: if you compared the pictures from the two lenses side-by-side, you'd be able to tell which picture was taken with the more expensive lens. But if you looked at the expensive lens' picture in isolation, you'd probably still say that it was not sharp enough).

• First of all, you're really far away. You're so far away that (in the 15mm example photo) people are only about 50 pixels high, and the letters on the sign are only about 15 pixels high. 15 pixels isn't a lot of room to make sharp letters anyway, but if you want sharp letters you'd need enough detail to be able to see the expression on the pedestrians' faces. In the 85mm example, where the letters on the sign are much sharper, I can almost make out the expression on the face of the person walking underneath it. When you zoom out to 15mm, you're trading sharpness (resolution) at any one point for a wider view of the scene.

• It looks like there's a lot of moisture in the air. That means some haze, and since you're so far away from the subject, that means you're going to lose some sharpness.

• There isn't a lot of contrast in the sign itself. You have good exposure for the photograph as a whole, but by looking at just the sharpness of the sign, you're getting a little misled because the sign is a little muted:

• You used the Neutral picture style. That means your camera didn't do any sharpening at all. You should try sharpening the picture a little bit, and see if it looks better.

• You're being really picky! (I am, too, when I look at my pictures. There's nothing wrong with that. But you have to know when to let it go.) When I expand the original (15mm) picture to fill my 15-inch widescreen-ish laptop screen, it looks nice and sharp across the entire picture. That's roughly the same size as an 8x12" print. Zooming in to get a 100% crop means zooming in about 4x. That would be a gigantic 32x48" (80x120cm) print! Unless you really need to print or view your pictures BIG, don't worry about how they look at 100%: you'd have to get your nose right up to the picture and really concentrate in order to see those defects.

So, how to improve your pictures:

• Get closer! "Fill the frame" is common advice for a reason. Either get closer (preferably) or zoom way in (not as good as getting closer, since you'll be shooting through more atmosphere). If you still need the really wide view, you can try to take several pictures and combine them to get your panorama.

• Sharpen your photos with post-processing. Either yourself, using software on your computer, or have your camera do it with a different picture style. Don't expect miracles, but it should look a little better.

• Look at the picture as a whole, instead of zooming in to 100% to examine details. If you're heavily cropping your photos, you're probably using the wrong focal length. Get closer or zoom in more (or get a longer lens).

• Remember to expose correctly. That means expose your test subject correctly. If your test subject is just a very small part of the overall frame, make sure that little bit is exposed correctly, and don't worry about the rest of the picture. This is different from when you're shooting in the field and you want the entire photo to have a correct, consistent exposure.

• Choose subjects that play to the strengths of your lens. If straight lines and sharp angles (like letters on a sign) look a little fuzzy, take pictures of things that don't have straight lines and sharp angles. Nature photographs won't have straight lines in them, so if you're planning on using this lens to shoot waterfalls then be sure to use waterfalls for your test shots.

And one more thing: you said, I had read a lot about the sharpness of the lens on the wide end in the reviews, and it seemed odd to me that the longer end was sharper for me, but that's not what you were testing with your sample pictures. By standing in one spot and zooming in and out, you were testing the change in field of view as you zoomed your lens. If you really want to compare sharpness at 15mm to sharpness at 85mm, you need to make sure that your test subject is the same size on the sensor at each focal length. So:

• take a quick look at this answer, then try to do the same thing with your lens. A car might make a good example: get up close to it, and "fill the frame" with the car at 15mm. Then zoom out to 30mm, and walk backwards until the car is the same size in your viewfinder, and take the next picture. Keep zooming out and walking backwards until you get your 85mm picture with the car the same size in the viewfinder as in the 15mm picture. Now it's okay to compare sharpness at different focal lengths, since each object in the frame (like a side-view mirror, or a handle, or a headlight) should be about the same size in pixels.