This app is quite helpful, but I believe it would be even more helpful if I had about 30 seconds' warning before my screen started to dim. A notification (using Growl or Notification Center) saying "break will start in 30 seconds" would let me finish typing my current sentence, or whatever, and be less likely to hit the "postpone" button when the break actually starts.
Re: Feature request: warning before break
Yes, that would be a very useful feature... and it is planned for version 2.