Beeminder is, so far, perfect for me. After pushing the free plan to its generous limits I decided to spring for Infinibee to setup a large number of plans, as Beeminder replaces Habitica for me as my daily task planner. I’ve been a loyal Habitica user for years, but while the carrot worked great for to-dos, there was never a strong disincentive to avoid failing tasks.
Habitica would give you a “perfect day” if you finished all of your todos that repeat every day, as dailies, but over more than a few years of usage I never got more than a few dozen “perfect days”, despite being tasks I knew I needed to do every day!
It did an okay job at prioritizing long term goals in making todos that had laid stagnant longer worth more points, but Beeminder does such a good job of breaking down long term goals into short, daily, actionable bites, and it can especially handle well tasks that occur at a rate different than once every day! What an incredible tool! Since I started using Beeminder, I’ve been getting the Habitica equivalent of “perfect days” nearly every day, and when I work ahead I feel better the next day taking some time off knowing I’m on track!
My first derailment happened today - I set a goal to stop overeating in my dieting app. But, frankly, looking back on how much work I have gotten done because of Beeminder just in the past week I can definitely join the loyal crowd of people who profess that Beeminder has definitely derived me more than enough value for the price!
I have to say, though, as a student with limited income the 5$ derailments are already incredibly terrifying enough for keeping me on track for almost anything in my book. 
I love this chart where you can see when I start using Beeminder after switching from Habitica in Anki.
Cheers!
