First - I must say I'm pleased as punch with the current progress. While it's slow going I'm VERY satisfied with my investment considering the low cost of the engine (I've spent a 1/10th of what I planned initially when shopping around). I cannot fault your work despite the minor issues from time to time.

There are a few things though that need worked out for this engine to really shine.

1) This is pretty much non-negotiable. The file management system needs a complete overhaul. There should be a search and grouping system. The search is straightforward. The problem I have is when you purchase items, you cannot go and move them around inside of the editor to a more logical grouping (such as per level, per type, per genre, etc). Even if you do it outside, the game engine simply downloads them again next time, negating your work to order and sort - while also making a duplicate that eats HD space). A bare bones search would make this a little easier. Meta tags on the objects imported from the store (then searchable) would also help. Ideally a full file system manager would be the real solution but I realize that's not a priority. So just a simple search hacked in there would be enough for now.
2) Raycasting. I'm not saying from the standpoint of the engine itself casting rays for scenes but rather the ability to trace a ray would be hugely beneficial from a LUA perspective. There's a lot of nuance to AI/fuzzy logic that can be done with this.
3) Positional audio for characters. I'm not sure if I just don't know how to do it, but this is a massively frustrating thing for me to hear zombies making noises as if they're standing right next to me when they're 2000 units away.
4) The ability to pass a few flags/variables to objects from the editor. Example - let's say on the properties you have 4-10 'value1,value2,value3' etc fields. These fields only take an integer up from 0-255. This then shows up in lua as a directly accessible item such as 'entity.value1' or something. From which much manipulation can be done, you dig? This I don't feel should be a significant amount of work but not knowing your backend, who is to say?
5) And lastly - the ability to turn off sunlight shining indoors.

I realize there are a lot of huge ticket items out there and with dx11 coming the logic is 'this can be fixed in dx11' - except much of what I'm asking for is something that can be added in the course of a week or weekend which will GREATLY improve the functionality of this game engine in the near term while we wait the many months for DX11 to be implemented, tested, bugfixed, etc.