Despite numerous websites covering this topic a few days ago, I have written this post late for a reason -- to actually look at the updated product instead of just covering news about it.
Now for some backstory. Way back a few months ago, Outlook.com was launched in its beta phase. Other services such as Contacts (People) and SkyDrive also received a refreshed user interface based on the one that Outlook.com is using. However, the only thing that was not updated until now, months after the public (stable) launch of Outlook.com
For those that don't know Calendar has always been a product to get updated later than others, and it's actually traced back to a messier, more cluttered code base from the original calendar. I've also seen reports about the Calendar team back then being disbanded, but I won't argue that its factual since I haven't hard of this many times.
The new Calendar, which should be available now to just about everyone, is completely new. The entire service has been completely rewritten, which brings numerous benefits such as a much more organized and neater code base (which is always good).
However, which all of the back story and interesting news aside, it is still the same calendar. The new Outlook.com Calendar doesn't really have a golden feature that another calendar service wouldn't have, but however the new Calendar is cleaner, giving more room to the actual calendar part of the web page.
Options for the calendar is found similarly like other Microsoft services, which will be in the cog menu at the top, near your name. There you can adjust your weather, manage calendars, and more. The weather part is actually pretty serious as for those who used Outlook.com before, to change the weather you would have to visit the Hotmail themes page, which you couldn't get in Outlook.com. The calendar update fixes this issue.
Below is a picture of my Outlook.com Calendar. I have multiple calendar feeds, which are color coded. You can click the image to view it larger, which I recommend you do. However from the (shrinked) photo below, you can see that tabs like the views have been merged into a drop-down, which saves space and allows more room for the calendar.
One feature that I like about the Calendar in this update is the one-click adding of events. All you have to do is click a date and a small popup displays, allowing you to enter info about an event or an advanced (full) view of creating an event to add more advanced options.
Like I have said before, just about everyone should have this update by now. If you don't, wait just a few more days and it should arrive soon. Microsoft has said that they were gradually rolling out the update over this past week.