What are the advantages of a macro lens?

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I have been charged with developing a large brochure/booklet for my company. This will consist of a multitude of product photos. My question is: What are the advantages of using a macro lens over a conventional lens? Obviously I have not done much macro work. I am thinking about purchasing a macro lens (either the 100mm f/2.8, or 180mm f/3.5) but want a better understanding of the advantages.

Here is a shot that I took using my 17-55 f/2.8 IS which represents the type of images I am talking about.

http://www.dykstra.us/images/IMG_9616.jpg

[Davidoff]

A macro lens allows you to focus much closer and get a higher magnification ratio ( 1:1 ). If you want that kind of shot, just use what you have, if you need to get closer, get the macro lens.

[Canon Bob]

If the shallow depth of field, as shown in the keyboard shot, is acceptable then any lens with close enough focus will probably do. If you need to get more of the subject in focus then I suggest that you look at one of the TS-E lenses.....24, 45 or 90 depending what size your subjects will be.

Bob

[JeffreyG]

I agree with Bob, if you don't need to get closer than the sample image then look hard at the 90mm TS-E. The total control of DOF would seem to be useful for product shots.

If you need to get a lot closer than the sample image then you need a macro lens.

You need a good tripod to use either.