On the upside, the OS is said to have full Xbox gaming integration (including gamertags, avatars and, yes, achievements), full Zune integration, full support for social networking, and a try before you buy system in the Marketplace. What we apparently won't be seeing at MWC, however, is any Windows Phone 7 hardware, as the announcement is said to focus solely on the user interface. According to PPCGeeks, however, Microsoft is confident that the first hardware will be ready by September of this year. Hit up the link below for the complete rundown.
Update: MobileTechWorld looks to have also received the same batch of rumors, and has revealed a few more, including word that the browsing experience is currently "better / faster" than the iPhone 3G, and that Microsoft is "aiming towards" the 3GS. They also say that while there will be no Microsoft-made device, the company will have tighter control of the manufacturing process, which promises to simplify things for everyone involved and allow for over-the-air updates.
Microsoft Windows Mobile 6.5
Microsoft Windows Phone 7
Microsoft Windows Phone 8.1