I don't know how many of you are aware of this blog, but I have been following it for quite a while now. Link is
http://dailly.blogspot.com/. Its the blog for GM's programmer that YYG hired to write runner in C++ and port GM to other platforms. There is some interesting technical details, even thou they are not that complicated (as they are meant for the layman I suppose). And there he writes about many aspect GM and in turn Enigma has either implemented, it is going to implement, or should implement.
1) First things first - Texture packing. I am aware that Josh is using some rectangle packing algorithm (or he is developing his own) for fonts. What Enigma should also do would be packing as many sprites/backgrounds inside one texture as well. Mike (that's the name of that guy) posted on how GM now uses that to launch on devices with limited GPU speed and memory. Pluses for this are quite obvious - there would be a lot less texture switching, and the amount of memory used would also decrease substantially. Enigma already uses spr2d->texbordx and spr2d->texbordy to get the point where sprite has its width and height and so the rest of the texture is not needed. With texture packing there wouldn't be that much things to add, except spr2d->texbord_left and spr2d->texbord_top or something similar. Then the drawing functions could be changed easily to accommodate that. Like setting every texture size to 512x512 (something every GPU, even mobile device should support), and then packing as many images in that 512x512 as possible.
2) Next he speaks about many aspect of GM and how it could be improved by using types (Enigma already supports thous), structs (Enigma doesn't supports them for now, or ever or I am wrong) and some other stuff. From previous posts I get that he would want to implement them, but they don't plan to do that for now (because Mark wants his tool to still be very easy). Thou he showed that it wouldn't change anything in GML (just like in Enigma), so if you don't want to use types, then don't and it automatically uses doubles, but if you really know what you are doing then you can easily declare an int.
Anyway, there are more things. I don't think that we should denigrate (is that the word?) that guy because he works in the Evil YYG. There are many things we can learn about GM future development, and in turn, it could affect our development as well.