The Nikkor 18-105mm DX AF-S Zoom lens f1:3.5~5.6G ED VR lens is a kit lens that comes with the Nikon D90 and other mid-priced amateur cameras. It is an overall lens with a farily large zoom range, and is often the most used lens in your bag. It includes Vibration Reduction, a mechanical system to reduce camera shake at low shutter speeds.
Overview: This is a marginal lens for advanced amateurs, however it is kitted with many camera bodies, including the Nikon D90, and I only own it because it came with the camera as a kit. In retrospect, I should have purchased the D90 as a body only. There are better lenses in this focal length, and it is a candidate for replacement. A better lens was the 18-70mm kit lens that came with the Nikon D70, but it is a bit harder to find these days.
I classify this lens as entry level, as it features a PLASTIC mounting ring, which is hardly worthy of camera equipment. I cannot understand why Nikon would not make a metal mount, only to save a few pennies, and this is the primary reason I dislike the lens. In addition the lens is quite slow, especially at the upper telephoto end where the maximum aperature is a paltry f5.6. As this is intended to be the most-used lens, the tiny aperature is a significant disadvantage. A far better lens in my view is the Sigma 18~50mm f2.8 zoom lens. It maintains f2.8 throughout the entire zoom range, which is one hallmark of a better lens. Although it tops out at 50mm, you have a huge disadvantage using the Nikon lens at 105mm anyway as that is where the aperature is restricted.
Since the aperature of the Nikkor 18-105mm lens at 18mm is a respectible f3.5, staying in the wide angle range of the lens will result in better low-light performance.
The Nikon alternatives are little and far between. The Nikkor 18-200mm zoom lens is marginally better. While it has the same aperature rane, the lens mounting ring is at least made of metal. The only real Nikkor alternative lens in the DX format is the super expensive 17-55mm f2.8 lens, but at a much higher cost than the Sigma alternative. This is not to say that you cannot use the Nikkor 18-105mm lens, but due to the aperature limitation, you will not be doing any low-light photography.
This lens is AF-S focusing, so that virtually all Nikon DSLRs will work with this lens in autofocus mode.
Alternatives: Another option is to obtain a nice super wide-angle lens like the Tokina 11-16mm f2.8 zoom lens, coupled with a Nikkor 55mm f1.8 lens and forego the 18-105mm zoom lens altogether. However, this means more lens changing and lugging around more hardware. In the cruise environment, you may wish to travel light - especially during excursions, so if you intend to shoot mostly daylight, the 18-105mm lens may prove to be acceptable regardless of its small aperature.
The lens features Vibration Reduction, which aids in slow shutter speed photography. Often you can extend the shutter speed down to 1/15th of a second without the need for a tripod or monopod. It should be noted that Vibration Reduction aids in camera shake - and will not help to keep the subject in sharp focus.
18mm wide angle photo of harbor entrance fort - St. Thomas, USVI
105mm telephoto photo of harbor entrance fort - St. Thomas, USVI
Summary: While this is not the best choice for the major lens for your camera, the alternatives are more expensive. This lens would be completely satisfactory if it were intended to be occasionally used (save the plastic mount). However, for the lens intended to be used most often, a slow lens such as this will be difficult to use in low light conditions. If you have to use the lens in low light conditions, try to limit its use to the wider-angle settings as the aperature is significantly larger at the low end. Consideration should be given to replacing the lens with a faster version if you can afford it.