Apple made two significant design changes to iCal in OS X Lion — a leather-like toolbar and the removal of the calendar source list in the left sidebar.

The leather toolbar is an eyesore but doesn’t affect the core functionality. The absence of a source list, however, removes some critical features and hinders productivity.

Here’s how the source list differs between iCal and BusyCal.

Source List

The source list displays a list of calendars that can be checked on/off to show/hide events in your calendar. It also functions as a color key, so you can tell at a glance that the blue events are on your Work calendar and the green events are on your Family calendar.

To see the source list in iCal, you have to click the Calendars button, which displays a popup window that obscures the calendar behind it and cannot be moved or resized. It is not possible to tell what calendars are being displayed or the calendars that events are stored on without clicking the Calendars button.

In BusyCal, the source list is permanently displayed in the left sidebar so you can see all of your calendars and their colors at a glance without any clicking required. And when an event in selected in your calendar, its parent calendar is highlighted in the source list, providing a visual indicator of where the event is stored. 
In addition, the BusyCal source list provides two key features — Calendar Groups and Mini-Months — that are no longer available in iCal.

Calendar Groups

Calendar Groups allow you to arrange calendars into collapsible groups that can be shown or hidden by clicking a single checkbox. This is a convenient way to group all of your work related calendars together, and your personal calendars together, and show or hide an entire group with one click.

In iCal, you can create Calendar Groups for local calendars, but you cannot create them for MobileMe calendars or any other service. BusyCal lets you create Calendar Groups on any service (local, MobileMe, Google, WebDAV, etc.).

Mini-Months

A Mini-Month is a miniature monthly calendar that is useful for viewing past or future dates or navigating to a specific date.

iCal only displays the mini-month in the Day View, and only shows a single month. BusyCal displays the mini-month in all views and can show multiple months, if desired.

Calendar Groups and Mini-Months did not exist in BusyCal 1.0 but they were so heavily requested that we immediately added them in the 1.1 and 1.2 updates. It’s ironic that these two features, which existed previously in iCal and were added to BusyCal due to popular demand, have been completely removed from Lion iCal.

Try BusyCal

If you recently upgraded to Lion iCal and are missing the source list, calendar groups, and/or mini-months, you may want to give BusyCal a try. You’ll find that it includes more of the things you like about iCal, and less of the things you don’t.