The single necessary feature that the web calendar lacks is the option to enable infinite scrolling (much like the osx Calendar app). I constantly find myself toggling back and fourth between months, like at the end of this current month, where I see Saturday but Sunday (May 1).
And the ability to forward an event. And the ability to propose a new time for a meeting. And the ability to accept a new proposed time for a meeting from a client that does have that ability.
The ability for event colours to actually be labels (that can be filtered for visibility) would be appreciated, currently you have to setup multiple calendars to achieve this, and that's not too useful if people are trying to track when you're free/busy.
Thats a good point. It does have find times, but a lot of the other recent feature launches aren't there like goals and the event creation auto complete.