HTML Email Approval

I would like to connect with anyone who is currently using the HTML Email Approval process. We would like to create a custom HTML Email Approval for a custom time entry screen. The recipient email addresses for the HTML Email Approval would not be within our email domain and as such we may be sending emails to various domains. The hope would be to streamline the custom timesheet approval process we have in place now and allow the approvers to approve directly from their email rather than logging into the system to do the approval.

If you're using this today I would like to get your feedback. From what I read this should be possible but wanted to get some real world input.