Here is an excerpt that in my opinion shows how disconnected from reality the open source crowd can get...
The sales cycle of a traditional enterprise vendor is just too long. It takes several months to get the right sales meetings, convince the CIO, sign a deal, do a pilot - maybe the customer spends a little money at this point but not much - evaluate it, follow it with a beta phase, and then hope for a real sale. That's one and a half years to get the deal. All along, the software vendor is convincing the customer to buy.
Back at the company that deployed the Open Source solution, the CIO is happy with the software. But after using it for a while, begins to wish for documentation, a live-person to ask questions, a phone number for support, and so on. At that point, the customer calls the company saying, "I've been using your product for a year and now I need your help."
So, the company was able to do a successful implementation of the enterprise software without documentation or support, but then after "using it for a while" they decide that documentation and support would be nice. Anyone who knows the enterprise software business knows that the implementation phase is the most critical part where it is essential to have people who have an indepth knowledge of the software to assist the company through the difficult process of deploying a mission critical application.
In reality, I don't see how open source offers anything more than an evaluation version of a commercial application does when it comes to reducing sales and marketing costs. Don't tell me that Firefox has not had to do extensive marketing to get to where they are...
The scary part of the above quote is the inference that with open source software you can get it in the back door without the approval of the CIO, get it working in a skunkworks project and then reveal a wonderful working solution to management. This may work for hosting the company website on Apache but I think the auditors may get a bit nervous when you change the accounting system without approval.
The best benefit to Open Source that I have seen came from Frank's survey that people really care about vendor independance.