Customer: Who is my business relationship with?
Your ultimate concerns are with your shareholders first, and your customers.
Customer: Who do I sue when the product can't deliver the expected functionality?
If you look for an off the shelf solution, you fire your IT manager - If you have purchased a bespoked product, then your legal manager should advise (if not, fire him too).
Customer: How do I train my people to use this new software?
Using something like KDE as a windows type environment, retraining is minimal when looking at basic office apps. What bright spark uses that abomination called Powerpoint anyway...
One way to tackle the task of selling linux is to talk about the "total cost of ownership" - MS license per machine @ ££££ + ongoing training costs and additionl fees for virus scanner upgrades etc, etc... Linux - Small one off cost for initial retraining + ongoing training costs - Virus protection is not such an issue. Both options incur some IT support costs - Linux has great potential to reduce these and in so doing, improve the company profit margin.
Then point to examples of linux in use - Hill Hammond installed a wide area network of linux boxes in most of their branches at a much lower cost than a MS solution.
Just my 5p worth (after inflation).
Regards, Paul.