Fuel injection cleaners?

Whats the deal with fuel injection cleaners/additives? Do they work? are there any drawbacks? Is one brand better than any others?

We use the BG brand products at our shop. They seem to work wonders. The down side, is they are kind of pricey, and cannot be bought in regular parts stores.

http://www.storesonline.com/site/598452/product/DI208

with instructions:

http://www.storesonline.com/site/598452/product/SMI001

Has been recommended to me