It appears that there are quite a few complaints on the forums about Magento being slow and this is probably true with an out of the box installation. There are quite a few things that can be done to improve things and response time in general.
With a switch to nginx as well as tuning of various components, the response time subsequently dropped by over half to about 4 seconds which is in the sweet spot for ecommerce sites.
The following are some of the changes made:
- Switch to using nginx as a front end.
- Set Expires to far in the future
- Utilize PHP FPM.
- Implement APC
- PHP tuning
- MySQL tuning
And Finally Test your site response using the tool http://tools.pingdom.com/