Don't worry, I'm seeing all of your edits, but there's a lot (which is really great -- I feel I'm learning a lot this time around especially) but I can only fix/edit/respond per each recommendation as I incorporate it

Anyways here's what had this morning, and after about 30 minutes of tinkering this is what I have now:

I apologize for the 2x zoom on this, but that's how I'm planning on displaying it eventually on dA/PJ; so, I'm trying to look at it at the right zoom level throughout the whole process to keep in mind that idea.
@jengy: At first I thought your suggestion was dumb, since I had the anatomy right already... but then I realized how wonderful your idea was. You'll notice that I rounded out the butt more in my latest quick edit, and it looks a lot more interesting now. I've never taken any art classes before, so I have next to no teaching on perspective (I'm going to fix that this summer however!), but from that simple edit you made I feel I've already learned to think in more of a cross-planar way, so that every plane (i.e. the one created by the back legs/butt, the side of her coat, the ones created by the sections of her face) works together with the other planes in a fluid motion.
@yaomon17: not exactly the style I'm going for, but I find it interesting how you shaded the tail in general (same with the mane), it'll help me when I finally get around to taking what has been Ai's suggestion for a few posts now and make it into reality

@Ai: Not a fan of the dithering in the shadow, but I think I may have to add a darker shadow shade in there somewhere to define it better. Thanks for the tips on the colors, it prompted me to "research" into color theory at school today, and I changed the palette around a lot. I think that after this edit that I've gotten much better at picking colors with the H/S/L values, and I've realized that I was using insanely saturated colors (and I played with them as a result). I didn't like how you used blue as the outline, I settled with more of a color that had a hue closer to the orange color (it ended up being something like a hue of 230 IIRC) and I think it's a bit less radical against the orange while still having the shadowy effect.
@Regulus Awesome: I would do MLP-styled clouds, but first of all those are really simple and boring (IMHO), and I want to kind of place Scootaloo in a bit more realistic environment ^_^
As for what I know I still need to do for sure:
- Anti-alias clouds completely
- FIX HER TAIL!

(been lazy on this one, I'll admit)
- Anti-alias different shades in Scootaloo, A-A her against the BG very slightly
, and selout her outline (on second thought... just read a few topics here about selout. Probably not a good idea to use it for this, or really at all. Helm seems to condemn it for making ugly pixel art, and from the insight he gave I'm just dropping the idea)
- make the water actually look like water, by adding some simple waves or something
- play around with her shadow some more
- fix up the cloud she's standing on
- a few birds in the background or something to fill up the space in the top left corner better (or maybe another cloud)
- maybe play around with her facial expression some more.
I think a fair gauge for the completedness of this is probably around 60% ^_^ I'm excited with how this is turning out, and the incredible amount of things I'm learning from you guys. I honestly have no idea how I'd learn so fast without you.