OK, so maybe I'm just too picky or something but when I have my calendar side by side with the calendar in Outlook 2007 it just doesn't look the same at all. Part of this is because Outlook 2007 did some wildly crazy things with categories and stuff until it only barely supports the old 2003 method of thinking, around which the whole calendar control is based.

1. The Outlook 2007 Calendar has a scrollbar for the all day region, and a separate one for the rest of the calendar
2. The Outlook calendar has date range, navigation buttons, and search stuff at the top. While I wouldn't necessarily expect this to be implemented, especially not the search, the last time I tried to add controls above the current view, I got a funny red region I couldn't do a thing with.
3. The Outlook Calendar also has that great region at the bottom with a list of tasks due that day. Separate scrollbar AND gripper for this region.
4. Starting into drawing differences, the colored border for the current day has a line that separates the all day events from the events for the day. The line also shows at the bottom of the time area, before the gripper for the tasks region, and continues down the sides and along the bottom of the task region.
5. The drop shadow behind appointments is missing from the Codejock control.
6. The line separating the all day events from the day, and separating one day from another, is bolder on the Outlook control. I personally like the lighter look in the Codejock version but I mention it for completeness.
7. The fonts are the same. Letters are almost identical but the numbers make it obvious. The font used in Outlook is slightly wider and thinner, and is anti-aliased. Close match, darn close, but not quite. Any chance of loading the font Outlook is using from wherever they have it and using the current one if the other can't be found?
8. Outlook adds little up and down arrow watermarks when there is an additional appointment outside the visible area of the day.
9. There are similar next and previous tab thingies when no appointments exist on any visible day.
10. This cool little click to add appointment watermark thingie comes up when you hover over a cell for about a second. Pretty, but mostly useless. Again, to be complete.
11. Categories. Earlier versions of outlook colored using the label field. Now categories are used, and if you have several categories that have colors defined, you get boxes for each extra category.

Of the items above, the only ones that I care a lot about are the navigation buttons and the categories. The Categories amazingly still manage to behave a little bit in the Codejock calendar since I do sort of get the color for the task from the label field which is apparently still being maintained. The color is off however and looks especially wrong when additional categories exist.