I'll give you a code asap once I'm greenlit and you tell me what you think about it during gameplay, deal?
GM is great for 2D stuff. You can even do a lot of fancy effects now with shaders and surfaces etc. I use it for my game. You'll notice pretty quickly that even in GM most everything you do will be coding. It's super high level stuff of course, very abstracted, simplified and sometimes restrictive to the point of being almost infuriating. My number one advice is to never even touch the drag and drop stuff and quickly get yourself accustomed with GML. I haven't watched his stuff personally, but I heard great stuff about Shaun Spalding's tutorials:
https://www.youtube.com/user/999Greyfox
Also, just like with Unity (from what I'm hearing) you'll find that GM has its quirks that will drive you crazy and eventually you'll be making your own tools and workarounds inevitably. If you're making super twitchy stuff or just anything that demands pixel perfect movement, be prepared to work with framerate dependent timing for everything. Its delta time implementation is not great (though it isn't the only engine with that problem of course, last time I was messing with Construct, its implementation caused highly inconsistent calculations and movement with just the slightest framerate variation). Personally I use a combination of delta time for all the rhythm dependent/music synced stuff and framerate dependent logic for everything else.
One big plus to GM is that you can get a prototype going in very little time, especially if you use the built-in collision functions, drawing etc.
