I just tested it, and it works fine for me, forwarding to my gmail account within seconds after leaving a message.
Perhaps your email account is blocking the notes as spam, or there is some other issue with the email address you are using. If you have a non-gmail address, try adding it to Google Voice and test forwarding to that address. If you already ARE using a non-gmail address, then switch to a gmail address.
Create an entry in your email account's contacts list for Google Voicemail, with an email address of "voice-noreply@google.com" as one way to try to force your account to not treat the notes as spam.