The Nikon D700's DX crop mode is certainly useful. It allows you to reuse your old DX lenses, which no doubt represents a not inconsiderable investment on your part.
However, using DX crop mode is really difficult using Nikon's default settings. Many D700 photographers end up using it the wrong way. This is what Chai will be covering in this guide - how to effectively used the DX crop mode in the Nikon D700.