Does YoYo have any plans for targeted testing as opposed to the existing "report bugs as you go in everyday development" casual approach? Some features, such as Android and iOS extension support, are things that require skills not present in most GMS users. Without targeted testing from skilled users, the final v1.3 product may end up containing features that have received inadequate testing, if any at all.
I'm sure you've heard enough of my complaints about SVN on GMS, and it demonstrates exactly why the existing approach is a problem when it comes to verifying large-scale new features. When the SVN mechanism debuted in GM:HTML5, there was a severe lack of users with existing working knowledge of SVN, and with it a glut of user-end testing. The result? When real users started using it in GMS, they immediately ran into blockers and serious usability bugs that were not discovered or reported early, simply because the whole feature was not being actively tried out by anyone when first offered. Until recently, it was easily the most poorly done part of the entire GMS program.
For each new v1.3 feature, I suggest getting at least one or two dedicated/expert-level users who have experience in relevant subject areas as testers and KB article writers (e.g. graphic designers for vector graphics, native Android/iOS programmers for extensions, etc.). This allows user perspectives to enter the development process early in a balanced manner, and delegating bug-hunting and FAQ documentation to them allows a greater focus on fixing broken functionalities. Such experience will also allow these users to gain early experience using the new features, which would likely benefit their personal work and make them more valuable in team projects.
Personally, I am comfortable with targeting the debugger, new drawing events and recent fixes in the SVN integration, so sign me up if you are interested.