i agree with you. -1 for this tile seems excessive, especially on the newbie quilt. i didn't vote on this one, but here's why i think maybe they voted so low... at the top you turned the black you received into a hard horizontal line by going directly to the orange and blue used in your background. then on the other edges, the blue goes up near the edge and turns abruptly to orange. so even if your neighbors blend the orange successfully, the blue will delineate your tiles edges... as does the abrupt change from black to orange at the top.

so basically it's a blending problem i think. remember the idea of quilting is to hide your tiles edges, make it seamless so nobody can tell where your work starts or ends. apart from the minor blending issues, i like your artwork. when i started i was the absolute worst at making my tiles seamless and hidden. so i kinda recognize what your going through. just hang in there and work on blending. [as you work, maybe try to get the blend right first, then add the rest] ;o)

i think that may really be the core of it, just that the edges look really hard to blend to. i think that even if you just smudge the blue at the bottom out to the edges to get rid of that orange line, it'll help a lot.
I agree with raga's comment about the hard black line at the top too.