What's the best calendar option for a 50-person, Mac-based company? My company is currently very unhappy with our calendar software: Now Up-to-Date. It's consistently sluggish and unresponsive, has an unintuitive interface, has a habit of losing events, and doesn't integrate well with online calendars that some of the staff keep for personal calendars.

We are almost exclusively (but not entirely) a Mac-based shop, with most staff on newish MacBooks. We have 50 staff, and are continuing to grow. We need functionality that includes viewing other people's calendars, allowing for proxy access (ie, allow an assistant to edit their manager's calendar), online and offline functionality, and an integrative and intuitive interface, as well as good stability.

Do you have experience with other alternatives? Can anyone speak to specific experiences with other software?