Oh yeah, I'm pretty dreadful. I've only played like 25 matches online (never had XBL Gold before this game) and I did pretty well on my first day, mostly because out of my first 15 matches or so, I played about 12 Scorpion players. Now I've lost like 8 or 9 in a row, but I don't really have the time or energy to devote to practicing (other life responsibilities, etc).
I played MK3 and UMK3 to death, and most of my reactions in MK9 are the same as they were for MK3 (i.e., if I block a teleport, I immediately go for the uppercut, even if I could try for a combo). My timing and finger dexterity on combos is pretty sluggish (using the default 360 controller, but I'm not very good anyway), which is especially problematic on juggles that require precise dashing. If I can get a combo north of 25% damage, I feel like I did something totally awesome. The only character I can reliably combo with is Sub-Zero, and it's pretty much just 2 or 3 variations of the same basic setup.
When I play online, I like to pick different characters each time to keep things fresh and because I enjoy the casual atmosphere of not knowing your character all that well, but this usually backfires on me since most people tend to stick to their 2-3 characters that they know really well.
Oh well. I don't let it bug me too much. I love the crap out of MK and I keep playing. But I'll never, ever be anything more than a mediocre player competitively speaking.
Feel free to add me if you want some more casual competition.