Nice start... but before I buy this as an upgrade to Anxiety (which I donated to, but which after a nice launch has been at a complete standstill), there are a few things I'd like to see.
A few fairly minor suggestions:
1- Better contrast on displayed text for calendar and to-do items. I like how Today dynamically tries to find appealing text colors for each item background color, but I find its decisions to be too low-contrast for an application designed for quick glances. As it is, it's very zen, but my eyes hurt trying to read it.
2- Ability to control which calendars are shown (give me a list of my calendars -- local and subscribed -- in Today's preferences and let me check/uncheck them individually).
3- Ability to see tasks due "X days in the future" (and highlight them further as a due date approaches).
4- Ability to sort tasks by priority, due date, or some combination thereof.
5- A redesigned calendar/task entry panel that facilitates very fast entry. For example, keyboard navigation doesn't work now, as you can't tab to the Calendar pull-down menu, and picking start/stop datetimes isn't as quick as it could be with big popup calendars.
For now, I've been leaving iCal open on a second monitor (or on another Space), but with these improvements, Today could be a more powerful, concise way to keep an eye on things.