Selling is really nothing more than putting your goods and services into the hands of the people who need them. Really good salespeople are really good listeners, and are adept at finding out what people really want and giving it to them. Really bad salespeople are really bad listeners, and are constantly trying to tell the customers that what they want is what they have.
Virtually every hardware and software vendor has a policy related to green computing. This policy is really a sales pitch - this is what they think you want. This is a great system, except it relies upon one thing; you knowing what you want. Because if you don't know what you want out of a sustainable computing solution, you are apt to make bad purchasing decisions. Moreover, you are more likely to fall for a bad pitch, as the salesman will be trying to tell you what you want.
There are a lot of factors involved in making these decisions including costs, corporate image, user skills, etc. If you are commited to any sort of sustainable computing initiative, you should take the time to identify your priorities. Think that reusing equipment is the way to go? Read the Rethink policy from eBay. Want commit to eco-friendly hardware for marketing purposes? Examine the EPEAT registry and the policies of the big manufacturers. As usual, it will be rare to find a pitch from a company that doesn't benefits their own interests as well. That's fine, just make sure they are your interests. For example, if you are committed to moving to a thin-client solution, don't be persuaded to buy more desktops or maintenence contracts from Dell as they change their business model because they are losing money. Because as the sustainability battle heats up, there will be a lot of pitches, and its easy to go down swinging.