Tons of users use Facebook, GameCenter, and Google Play game services. These are essentials that gamers almost expect. Social platform integration is extremely important to small indie success. I personally think the only thing missing from AppGameKit is solid 3rd party SDK support for things like Facebook, Google Play, and other options for In App Purchases (I'd love to see OpenIAB here - would give us a ton of more options for monetization).
Spine's OK, but I doubt I'll ever use it and it has been a huge focus of v2 for many. The 2D engine for AppGameKit is pretty good, a library of nice sprite shaders would be awesome. Performance could always be better, but it is pretty good.
The reason I stay with AppGameKit vs another platform is that it is quick and easy to write in t1. I can prototype a game in a few hours. There is some social integration, but it is falling apart. My runner up is Unity and i falls short in a couple of areas:
1) I'd need to buy plugins for 3rd party extensions (IAP , Facebook, etc) - I'd pay for these with AppGameKit, but not ready to pay for them with Unity since I have to learn a new language (but C# is pretty simple)
2) There's no good way to use a world / percentage coordinate system with Unity. They do have a new UI system with anchoring that will solve most of my issues, but I really like to design with a solid fit-to-screen style of design vs. a cropped design. So that will actually take me more work in Unity vs AGK.
Not to mention the UI, encryption, and other tools I'd lose if I went to Unity. Plus Unity, like AppGameKit runs through OpenGL and NDK on Android, so many of the same performance issues exist, and even the issues that we have with keyboard input on android also happens a bit in Unity (though it seems they've fixed most of it).
So all these lovely extras like a new IDE and debugger are great, but my preference would be that monetization tools (yes social integration is included in as a monetization tool) should be focused on over specialty tools like Spine and a new IDE.
Either that or AppGameKit can simply adopt an approach that allows the end users to more easily modify the engine core, Xcode, and Android templates. That would be the simplest solution for them. Then WE the developers could essentially design plugins that allow extended features like Unity. This would be my preference as it would allow for earning opportunities from folks like us and relieve a bit of the pressure from AGK.
TGC is a small company so allowing and facilitating end user modification would be a great boon to their business model.