Here's something that you can't do on Windows Phone: search your calendar for past, current or future events.
Seems an odd omission, yet we'll chalk it up to the "we're too busy to add it in" pile along with the ability to add new contacts from Bing search. Speaking of, the developer who made Add to Contacts (and who also makes "I'm a WP7!") has a new app out that fixes that whole inability to search your Calendar events and it's straightforwardly called Calendar Search:
"Although your Windows Phone can connect and synchronize with all types of calendars, it’s impossible to search and take action on calendar meetings, appointments and events.
With Calendar Search, you can unlock the power of calendar searching, and search your meetings, event, and appointments, by date ranges, keywords, even specific accounts, and take action on this powerful information!"
We've been using it for the last few hours and it does what it says, no frills. In that sense, if you need this functionality and can't wait for Microsoft, the $0.99 for the app is well worth it. There's a free trial too and you can give it a go here in the Marketplace.