Whoever is implementing Oracle Fusion will definitely have to answer the following question;
Do you need to have the Oracle Fusion environment hosted on your premises or do you want to host with a third party or host this in Oracle via the Saas or OnDemand model?
To add some more complexity, Oracle provides you with option either to install the application on 'bare metal' or leverage Oracle Virtual Machines (OVM) to host all components.
Our experience has been that the fastest and easiest way to get going is if you use hosting service of Oracle or some third-party. However, the flip side of using a hosted applications is that you will see an increase in the turnaround time if you are upgrading, applying patches or debugging, which will be quite high in the initial days and you should keep a buffer for all these exigencies in your project plan.
The next best alternative is to use an on-premise OVM install. You can be up and running in 3 days. Internally at Wipro we are able to set up an environment using OVM install in less than 3 days. The last route is to go for a bare-metal install. This is quite a challenge from DBA perspective and can take well over 2 weeks to set up the environment. Oracle ships both bare-metal as well as OVM versions of the releases, so customers can choose either of these.