What's the point of putting together a to-do list if you're not going to follow through? The Reminders app in Mountain Lion vastly increases the chances you're going to cross more stuff off by the end of the day.
For starters, you can pin any list to your desktop just by double-clicking it, so you'll be less likely to ignore those tasks. Second — and this is a biggie for me — you can add a location to specific reminders. For example, just this morning I set a reminder to pick up my TransitChek chard for when I arrived at work, and my iPhone buzzed as I emerged from the subway. I have no excuses now.