One drawback preventing me from switching over completely to Numbers from Excel is its inability to create hyperlinks to local files. I work around this by serving the files on my local machine using Mac OS X's built-in Apache Web server.
First, turn on System Preferences » Sharing » Web Sharing. Test that the server is working by typing 'localhost' into the URL box of a web browser. An Apache message should appear confirming your Websever is functioning. Then add files to /Library/WebServer/Documents folder. Link this file to an entry in Numbers by highlighting the entry in the cell, then create a hyperlink in Numbers' Inspector by checking the 'Enable Hyperlink' box and in the 'Link to:' box type 'http://localhost/filename.' That's it.
To keep documents organized in their proper places, create aliases to the files in the WebServer Directory and place them where one would normally keep the file. For example, create file folder aliases for folders containing pdf copies of bills or receipts, for examples, and place them in your Documents folder for easy access to add/delete/modify those files within one's normal organization or workflow. Files will automatically update in their real location within the WebServer directory.
[crarko adds: I tested this, and it works as described. It's odd that Numbers doesn't support the file:// convention in a URL, but I tried it and it didn't work.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20101204103009390