Ease of creating and maintaining calendars that reflect my current, actual, finances as well as projections and goals - without being tied to a specific account.
You don't connect CalendarBudget to you existing bank accounts (wish I feel better about) so it requires spending the time to keep your calendar(s) up to date manually. I normally spend about an hour a week.
But, honestly, I don't understand how someone can keep a budget that doesn't project future income and expenses on the dates those actions occur. I use it for personal bookkeeping and it is not part of my day-job. But I manage my band, which I treat like a small business (albeit not a financially sound one!). Calendar Budget has been crucial to the tracking of my expenses/income there as well as at home.
I have used several applications designed to help me keep a budget but most, like Mint, are set up for you to create goals and direct accounts to those goals. They have no association with time. And my financial needs are time-based.
Calendar Budget uses actual calendars so I know, at all times, exactly what money is coming and going out. I can easily project future income and expenses - exactly when they will occur - and change them on the fly. I can have multiple calendars so one keeps a real-time look at my finances while others can be used to set goals realistically. If I anticipate a large purchase in 6 months I can plan out exactly how to be ready to cover it. If I know that I’m getting a good tax return I can estimate how much income it will be and exactly when I’ll receive it.
I enter what I actually spend and plug in items like bills, maintenance costs and discretionary spending - so if you want a maintenance-free product this is not for you. But if you want a tool that can tell you not just where you might be in 1-5 years, but how you are going to actually use and need money tomorrow, next week, next month, etc, then Calendar Budget is the best I've seen.