Microsoft Dynamics CRM is built using a number of different techniques and tools from Microsoft. Given these various techniques performance is optimized, but that does not mean that each individual partner, customer and developer doesn't need to pay attention.
Performance of a multi-user, highly dynamic, many moving parts system is worth adding to your project plan. To make fine tuning performance even easier the Microsoft CRM Engineering for Enterprise team has continued to keep their "Optimizing and Maintaining the Performance of Microsoft Dynamics CRM Clients" and their testing documentation such as the "Microsoft Dynamics CRM 2011 Performance and Scalability with Intel" white paper current.
There are even more resources when it comes to performance and Dynamics CRM so if this is a hot point for you, take a look!