Will I regret getting into this? No, no I will not.
Ky, I really like your style, the warmup had nice movement, especially for a sitting pose; and while I preach no "accepted" style of art since everyone has their own style, I advise taking into account at the noses. Many of the classes have convex noses (Scout and Engie are the two exceptions), so that would be something worth looking at.
Really, even if the nose thing doesn't work out, capturing the body language of the subject says a lot about that character anyway, and you seem to be pretty good at that. It's always good to have flow in a drawing.
Should you feel that you want to move to a more realistic style or proportioning/anatomy, I would recommend checking out this thread: http://tf2chan.net/workshop/res/22.html and looking at reference photos for poses and the relationship between body parts: how they move, length comparisons, etc.
Long story short, everything Ashe said. Derp.
Also, keep drawing and posting, Ky; don't be so hard on yourself.