Thought I give a short summary for you who are interested in bringing your WP7.5 app to WP8 for what you should look out for.
In general you shouldn’t recompile your WP7.5 app to WP8, for two reasons. Firstly, WP7.5 apps will work on WP8 as is, without any need to rework the code. Secondly, recompiling apps is only going to get you in trouble, because there are some changes in the way .NET Framework and CLR has been implemented on WP8 compared to WP7.5. There is a totally new kernel on WP8 and for example totally new garbage collector implementation on WP8. Also precision is not the same in all cases with WP7.X and WP8 with number handling.
What you should consider is to bring your app to Windows 8 with the same trouble, as now with the shared kernel and programming model (XAML+C#/C++) you are able to double your presence in the markets. We’ve been able to reuse pretty much 99% of the code in couple of titles we’ve done targeting Win8 and Windows Phone 8 platforms with C++ DX based games.
Windows Phone 8 will also include in-app purchasing , so finally you can bring additional paid content to your apps/games. Micro payments have proved to be a very efficient way to a developer to earn more money, as buying decision bar is much lower with small amounts, and there will be more purchases for items/features than you would expect with right kind of content.
These are just a tip of the iceberg, and when the NDA is lifted, I’ll talk more about other cool features that are hidden in the SDK, that will make WP8 rock!