I think encrypting cookies sounds like a great idea for two reasons:
if the information is sensitive, it would protect the information from snooping
it would make it difficult (impossible?) for visitors to your site to tamper with the cookie to try and exploit your site.
But yes it probably depends on what information you are storing in cookies. I would not recommend storing sensitive information there if you can avoid it. A session id is probably the most sensitive thing that you should ever put in a cookie.
You should probably configure your site so that you can turn off the cookie encryption if you want to. It would be super hard to troubleshoot any cookie-related problems with encrypted cookies.