I would suggest some tutorials for you... (not advertising, just helping) Check ImagenSkins and look up some GIMP tutorials, follow them and post the outcomes for some real CnC.
Well, GIMP is worse than PS. Text generally does not look good on a diagonal. The blue of the BG does not fit with the color of the panda. Since all the colors of the panda are neutral colors, I think that the BG should mirror that trend. The C4Ds are pretty randomly placed, and should be used to emphasize the flow of the image, not just to prettify it.
Gimps not worse than ps, its all in how you use it. Text doesn't look as good, usually, on diagonal. The c4d should be removed, and you should look up some tutorials, like RST said, they are very helpful for beginners.
Indeed, it is incontrovertible that GIMP is not an inferior to PS. It is at least 10x as user friendly, which makes up for most of the difference in pure power between the programs, additionally, it's open source, which is pretty much awesome. It all depends on how you use it.
RightSideTheory is correct. Listen to him, damn it. I gave you some helpful suggestions a couple of sigs back. Apparently, you didn't listen. Taking criticism and applying what you learned is a huge step in improving. I suggest you do that.