Having an orientation lock is a must have for the next update. Something so simple. Why it was not included when WP launched is beyond me. The phone is frustrating to use in bed or on laying on the lounge.

Please, provide a way to backup the texts.
Or, at least, provide a API access to the texts to allow developers to implement an application for SMS backing up.

It would be great if we will get some support for intercepting incoming calls and smss

Allow the BackgroundAudioPlayer to play tracks from the MediaLibrary. Or allow applications that implement the XNA MediaPlayer class to run in the background.

Modify the email launcher API to add an attachement

It would be beneficial to allow other messenger apps and social apps to come on board and allow their updates to show up in the people hub and messages to show up in the integrated messaging system. This would be great for any 3rd party app that has any social or messaging means to be able to leverage that kind of interconnectivity, example another IM provider (ex: Yahoo), social network provider, even apps for forum postings.

A business feature that would be really nice to have support for it the ability to tie into a VoIP network for voip phone calls... the most common architecture is the SIP (Session Initiation Protocol). So I would like the ability to configure a SIP client that ties into our VoIP PBX and phone system.. so my WP7 would basically become my desk phone (extension). The only way this would really work well is if it ran in the background like the phone's native phone functionality.

Allow users to choose if they want the "call/don't call" prompt dialog when an app invokes PhoneCallTask.

Fast dialing apps are killed by this limitation.

The same way a user can grant for background tasks, he could grant the app permissions to make direct dialing.

My country has banned facebook and twitter, which means i need use vpn 2 connect facebook.

Microsoft should expose GPS based API's that can trigger after say 5 min or 10 min departure from a specific GPS location. This would be very usefull in apps in customizing the reminders.

The TileSource class enables developers to provide custom tile sources for the Bing Maps control (such as OpenStreetMap), but requires an absolute URI to provide tiles. Given the frequently disconnected nature of WP7 applications, it would be better if it was possible to provide tiles from isolated storage to enable map downloading and access to maps when offline.

Please add full support for UPnP 1.1 / DLNA for third-party applications - perhaps even DPWS for potential future devices. The phone as a media / device controller is growing in popularity (ex: Sonos controllers).

For creating more contact centric views of contacts

We need to see more media formats supported......

Currently, when developing a alarm clock app, there is no way to tell if the user has his phone set to vibrate only, so a soundeffect set by the user is played even if he has set his phone to vibrate. I find this very confusing, even though the builtin alarm clock behaves the same way.
This would also be good to have for games, so when you launch a game in a quiet environment not all heads turn the user's way :)

Want to have a feature. Allows software products from the same Publisher, accessing IsolatedStorage. And can communicate with each other. Start each other (optional), which can be expanded larger developers ideas and more powerful than iOS and Android system.

This can save storage space, unified data storage location.

Or another form. Developers can provide their main program with subroutine. Subroutines can be run separately. Main program can manage/run program. In this way, developers can provide independent extension to process the data.

Wish to consider this kind of system design.

PS: above I use the online translation feature.

When you create a tile dynamically, it is common to want to save it as a Png file so that it uses transparency (so that it respects the theme accent color).
However, there is no built in method to save a WriteableBitmap as a png.
There is however a nice extension to save it to jpg, but that doesn't help if you want to use transparency to leverage the theme accent color in your tile.

I think many apps that need to generate a tile dynamically will encounter this issue.

Allow developers to implement an interface(s) on a user control and "submit" that instead of just filling in a tile data structure. This will make tiles truly "live" and open up the live of WP7 to new applications. This is also completely secure because the runtime can analyze the class (and it's IL) being submitted. A bevy of restrictions can also be heaped on the said user control in order to maintain performance and not sap battery life. Let Live tiles be live, please.