The key benefit of that approach is that you can easily tweak SubToMe to make it fit your design!
Here are three websites which did a great job:
- http://www.christophh.net/: a beautiful flat design button. Hard to not click to get more!
- http://continuations.com/: nice integration in the top menu bar.
- http://blog.izs.me: each post ends with an invitation to send an email or follow this blog. Nice call to action!
Did you put a SubToMe button on your site? Let us know in the comments.