Fixes
Marketplace - search, freezing, crashing, inability to update apps
Music & Videos - crashing
Xbox Live - inability to log in
Camera - save settings
Additions
Hidden Wifi Support
Podcast downloading OTA
Mirror Zune HD functionality on Windows Phone - Smart DJ, Rating Songs, Channels, Social (remember "welcome to the social"?) etc.
People - Search, Smart Dial, Categories or Group Tagging, More/Custom Entry Fields
Tasks
Unified Inbox
E-mail Flagging for Live/Hotmail Accounts
Custom Ringtones
Improve Volume Controls (System, Ringtones, Music)
Better Skydrive (and Live Sync/Mesh, Office 365/Live) Integration, especially for documents
Richer MS Office functionality and feature set
Bluetooth File Sharing
Bing - Image Search
Bing Maps - Public Transportation Directions
IE - folders for favorites, selective history deletion, url shortening
Twitter Integration
Screen Capture
Snooze Integrals for Alarms
Camera - timer, tap to focus; allow Windows Live Photo Gallery to see phone as device
Pictures - multiple deletion, support for tags, allow full resolution uploads on wifi
Manual wireless sync
Toast Notifications - allow them to queue up and be accessible until dismissed
Windows Media Center, doesn't necessarily have to be integrated into OS but an app with EPG, dvr and rich remote functionality (what ever happened to Side Screen or whatever that feature was?, WP7 should be able to function as a secondary browsing screen for WMC)
Xbox integration - WP7 should be able to serve as a remote and chatpad (especially considering that a large chunk of xbox customers use their device solely for media and non-gaming services)
Zune integration - rich remote functionality, similar to that of the iTunes app
Some of the integration features that I'd like to see might require a culture change at Microsoft but I expect better integration of their services, esp if they're going to leverage the Windows (7) brand. I also understand that additional functionality often presents an issue of complexity, which can be especially troublesome since "dumb phone" users are part of Microsoft's target market. However, the mark of an excellent UI is to offer rich functionality in a manner that is elegant and intuitive, not cumbersome. Functionality and easiness can coexist on WP7, so long as Microsoft is willing to put in the work.
I've been keeping a list, so I'll be back with more...