Recently our customers started to complain about poor performance on one of our servers. This contains multiple large CMS implementations and alot small websites using Sitef
Also, set your IIS to recycle the app_pool ONLY once a day at a specific time. I usually set mine for 3am. This way the application never goes to sleep, recycle or etc. Best to reduce spin up times.
Additionally configure IIS to 'always running' instead of 'on starup'. This way, when the application restarts, it recompiles immediately and again, is ready to roar.
Sitefinity is really a fantastic piece of software (hopefully my tips above get the thumbs up, and not my endorsement of the product). haha