Does API version matter when creating custom classes/triggers?

Question

I noticed you can choose/change which version of the Salesforce.com API when you create a class or trigger. Are there are benefits to using a new or older version?

Answer 1

Selecting a newer version will generally give you access to additional features, since the functionality available to your code is tied to the API version. To take a somewhat random example, the IsPartner field on Account can be updated in API version 16.0 and later. If you selected API version 15.0 or earlier for your code, IsPartner would be read-only.

The version number is there so your code doesn't break as Salesforce introduces new goodies. I can't think of a reason that you would pick an older version for new code, unless you're extending an existing system.