1) Hmmm... it's hard to tell from my perspective, but possibly SallyPants or EyePulp can help (they're Nikon people). I have stuck with Canon lenses for my Canon instead of going with a third party, but I imagine there's not a huge difference.

Usually with lenses, you get exactly what you pay for. The $200 range for an SLR lens like this is the bottom of the range. You could spend 10 times as much on one that looks the same on paper, but has clear advantages in the field.

Some drawbacks to lenses in the $200 price range are that they can require quite a bit of light (compared to higher-end lenses of course). Their auto-focus might be a bit slow as well.

However, if you are not using a high-end lens now, then you will not notice these problems. I have three lenses for my Canon, all of which are bottom of the line in their class. Pros would laugh at them, but for me, they're perfectly adequate.

All that said, I would find out what the difference is between those Sigma lenses. I don't know what "DL-M" or "APO-M" means, but I would bet that you would be fine with the cheaper of the two.

2) Same here, the DL-M and the APO-M was what I was wondering about as well and thought for sure someone might know.

3) Pastafarian might know; he's the technical side of our photography outfit 'round here. I'll direct him to this blog.

4) I have the Sigma APO lens (the 2nd one you list). It's OK for the money. For a low end zoom lens it will work. APO means Apochromatic - from the sigma website: "A: Apochromatic lenses are telephoto and telezoom type lenses which use special optical designs and optical materials (SLD or ELD glass) to improve their performance. The result is images which have greater contrast, sharpness and color definition than a comparable non-APO type lens . All Sigma apochromatic lenses are identified by the APO designation in their descriptions. Please see the Lens Chart for this and other specific lens information."

I think they are the exact same lenses mechanically with the APO version having a little higher end glass.

5) I'll be interested in this blog too since I'm ready to buy a zoom lens but looking at options to understand them better and of course working to get the best price for the lens that I can manage. I don't need top-of-the-line but I would like to get one with VR (Vibration Reduction) because I think that would be important to me. That does put me in a higher price area for the lens but I think I'd appreciate this feature. None of the ones above have that and the price makes it pretty clear too since the ones I have looked at were more in the $400 range.

6) I know I don't need anything super professional but as long as I am spending this kind of cash, I want it to be worth my while. So, maybe I should stick with the same brand for lens as well.

7) Like Dave, I am not familiar with Nikon cameras or lenses. I use a Canon Rebel XTi and recently purchased a mid-range 100 mm Canon macro lens. I am very pleased with the quality of this lens. Keep in mind, that when you get a lens, low end or high end in cost, your pictures aren't going to turn out automatically good just because you have a good lens. Macro shooting is tough! Light is an important factor but I find camera shake is the biggest problem. I have tried hand holding the camera for real close-up shots and it just doesn't work!!! Ninety-nine images out of a hundred will be blurry. I always use a tripod, legs not necessarily spread, but even with the legs closed there is some steadiness added to the camera.
When I do macro shots I use manual exposures so I can control exposure time and aperture; when working up close with subjects, light variation can change in just a couple millimeters. A big bonus for me is my camera allows me to take three pictures in one second with one press of the shutter button (or remote button - a highly recommended item) and each picture has a different exposure value (that I have preprogrammed) and the camera refocuses in between shots.

8) Thank you for all the great suggestions, luckily I have a tri-pod as well as a uni-pod (that came in handy for the bleachers during basketball and football games when my girls were in school).

One of my goals is for shooting distance while in Hawaii at my International competition as well as possibly some close up nature shots. I hope to make my decision soon so I can get it before I leave for my trip. I think I might be leaning towards the Sigma (APO) lens at this point. Again, I am not a professional and can't justify spending much more than I have to.