Initially I had held off on a review because there was a memory usage issue that I reported with version 2.1.0. That report and follow-up can be seen on the "Troubleshooting" tab.
Now that the memory problem is corrected, I'm happy to say that this is an excellent application. It delivers a great mix of functionality, ease of use, and aesthetics. It has one purpose and it serves it well; Timed breaks.
Personally, I'm using it to remind me to "take five" after every hour sitting in front of the computer. Just a five minute break every hour is making a significant difference to the way I feel while working. Prior to "Break Time", I could spend 10 hours in my chair, maybe getting up only once during that time.
The program itself is unobtrusive and has some nice touches that are missing from others in this category, such as: menu icon changes subtlety to let you know how much time before your next break, screen fade/lockout works across spaces, time remaining before next break can be adjusted on the fly, optional inactivity detection, plus others.
Finally, the author is a developer from a very well respected Mac application development company. I don't know if they know about this product venture, so I won't mention the company name, but it certainly made me feel confident in his abilities.