This is my painting of the dubbed FAQ Mech from the FAQ Page, This is my third attempt at drawing something and it's the first drawing I actually got around to completing, it took me about an hour in total, but over 2 days, Not the best, But id say it's pretty good for my crappy skill level. http://imgur.com/3BWVh
Looks fine to me, though I have to admit it is a different art style then the one you based it off of. I'm sure with a little bit of practice you could overcome whatever shortcomings you see in your art and reach a level that you feel content with.
I used a program called Paint tool SAI in combination with a Wacom 3rd Generation Bamboo Graphics Tablet.